Richard W.M. Jones
2019-Jul-24 12:17 UTC
[Libguestfs] [PATCH libnbd 0/3] Implement closure lifetimes.
This implements most of what I wrote here: https://www.redhat.com/archives/libguestfs/2019-July/msg00213.html
Richard W.M. Jones
2019-Jul-24 12:17 UTC
[Libguestfs] [PATCH libnbd 1/3] generator: Change Closure so it describes single callbacks.
In preparation for closure lifetimes, split up the Closure so it no
longer describes a list of closures, but a single callback.
This changes the API because functions which take 2 or more closures
now pass a separate user_data for each one.
---
docs/libnbd.pod | 3 +-
examples/strict-structured-reads.c | 2 +-
generator/generator | 760 ++++++++++++----------------
generator/states-reply-simple.c | 2 +-
generator/states-reply-structured.c | 8 +-
lib/internal.h | 3 +-
lib/rw.c | 32 +-
7 files changed, 364 insertions(+), 446 deletions(-)
diff --git a/docs/libnbd.pod b/docs/libnbd.pod
index 5608e63..631bb3b 100644
--- a/docs/libnbd.pod
+++ b/docs/libnbd.pod
@@ -487,8 +487,7 @@ C<nbd_set_debug_callback>,
C<nbd_pread_callback>). Libnbd can call
these functions while processing.
Callbacks have an opaque C<void *user_data> pointer. This is passed
-as the first parameter to the callback. libnbd functions that take
-two callback pointers share the same opaque data for both calls.
+as the first parameter to the callback.
The callbacks are invoked at a point where the libnbd lock is held; as
such, it is unsafe for the callback to call any C<nbd_*> APIs on the
diff --git a/examples/strict-structured-reads.c
b/examples/strict-structured-reads.c
index 92eb3e6..a50f662 100644
--- a/examples/strict-structured-reads.c
+++ b/examples/strict-structured-reads.c
@@ -225,7 +225,7 @@ main (int argc, char *argv[])
*d = (struct data) { .offset = offset, .count = maxsize, .flags = flags,
.remaining = r, };
if (nbd_aio_pread_structured_callback (nbd, buf, sizeof buf, offset,
- read_chunk, read_verify, d,
+ read_chunk, d, read_verify, d,
flags) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
diff --git a/generator/generator b/generator/generator
index fdacd71..3b57713 100755
--- a/generator/generator
+++ b/generator/generator
@@ -849,10 +849,10 @@ and arg written by the
function *)
| BytesPersistIn of string * string (* same as above, but buffer persists *)
| BytesPersistOut of string * string
-| Closure of bool * closure list (* void *opaque + one or more closures
- flag if true means callbacks persist
- in the handle, false means they only
- exist during the function call *)
+| Closure of bool * closure (* function pointer + void *opaque
+ flag if true means callbacks persist
+ in the handle, false means they only
+ exist during the function call *)
| Flags of string (* NBD_CMD_FLAG_* flags *)
| Int of string (* small int *)
| Int64 of string (* 64 bit signed int *)
@@ -921,8 +921,8 @@ Return the state of the debug flag on this handle.";
"set_debug_callback", {
default_call with
args = [ Closure (true,
- [{ cbname="debug_fn";
- cbargs=[String "context"; String
"msg"] }]) ];
+ { cbname="debug_fn";
+ cbargs=[String "context"; String
"msg"] }) ];
ret = RErr;
shortdesc = "set the debug callback";
longdesc = "\
@@ -1351,10 +1351,10 @@ protocol extensions).";
default_call with
args = [ BytesOut ("buf", "count"); UInt64
"offset";
Closure (false,
- [{ cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset"; Int
"status";
- Mutable (Int "error")] }]);
+ { cbname="chunk";
+ cbargs=[BytesIn ("subbuf",
"count");
+ UInt64 "offset"; Int
"status";
+ Mutable (Int "error")] });
Flags "flags" ];
ret = RErr;
permitted_states = [ Connected ];
@@ -1542,12 +1542,12 @@ punching a hole.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (false,
- [{ cbname="extent";
- cbargs=[String "metacontext";
- UInt64 "offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")]} ]);
+ { cbname="extent";
+ cbargs=[String "metacontext";
+ UInt64 "offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")]} );
Flags "flags" ];
ret = RErr;
permitted_states = [ Connected ];
@@ -1726,8 +1726,8 @@ C<nbd_pread>.";
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")] } ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")] } );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1756,11 +1756,11 @@ cause a deadlock.";
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
Closure (true,
- [{ cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset";
- Int "status";
- Mutable (Int "error");]} ]);
+ { cbname="chunk";
+ cbargs=[BytesIn ("subbuf",
"count");
+ UInt64 "offset";
+ Int "status";
+ Mutable (Int "error");]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1778,14 +1778,15 @@ documented in C<nbd_pread_structured>.";
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
Closure (true,
- [{ cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset";
- Int "status";
- Mutable (Int "error"); ]};
- { cbname="callback";
- cbargs=[Int64 "cookie";
- Mutable (Int "error"); ]} ]);
+ { cbname="chunk";
+ cbargs=[BytesIn ("subbuf",
"count");
+ UInt64 "offset";
+ Int "status";
+ Mutable (Int "error"); ]});
+ Closure (true,
+ { cbname="callback";
+ cbargs=[Int64 "cookie";
+ Mutable (Int "error"); ]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1829,8 +1830,8 @@ C<nbd_pwrite>.";
default_call with
args = [ BytesPersistIn ("buf", "count"); UInt64
"offset";
Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1894,8 +1895,8 @@ Parameters behave as documented in
C<nbd_flush>.";
"aio_flush_callback", {
default_call with
args = [ Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1937,8 +1938,8 @@ Parameters behave as documented in
C<nbd_trim>.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1980,8 +1981,8 @@ Parameters behave as documented in
C<nbd_cache>.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2023,8 +2024,8 @@ Parameters behave as documented in
C<nbd_zero>.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (true,
- [{ cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2052,11 +2053,11 @@ cause a deadlock.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (true,
- [{ cbname="extent";
- cbargs=[String "metacontext"; UInt64
"offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")] } ]);
+ { cbname="extent";
+ cbargs=[String "metacontext"; UInt64
"offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")] } );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2073,13 +2074,14 @@ Parameters behave as documented in
C<nbd_block_status>.";
default_call with
args = [ UInt64 "count"; UInt64 "offset";
Closure (true,
- [{ cbname="extent";
- cbargs=[String "metacontext"; UInt64
"offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")]};
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} ]);
+ { cbname="extent";
+ cbargs=[String "metacontext"; UInt64
"offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")]});
+ Closure (true,
+ { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -3137,20 +3139,6 @@ let () name
) handle_calls;
- (* Closure also must appear only once, but can be anywhere. *)
- List.iter (
- fun (name, { args }) ->
- let rec loop = function
- | [] -> ()
- | Closure _ :: xs ->
- if List.exists (function Closure _ -> true | _ -> false) xs
then
- failwithf "%s: Closure must appear only once" name
- | x :: xs ->
- loop xs
- in
- loop args
- ) handle_calls;
-
(* !may_set_error is incompatible with permitted_states != [] because
* an incorrect state will result in set_error being called by the
* generated wrapper.
@@ -3186,8 +3174,7 @@ let rec name_of_arg = function
| BytesOut (n, len) -> [n; len]
| BytesPersistIn (n, len) -> [n; len]
| BytesPersistOut (n, len) -> [n; len]
-| Closure (_, closures) ->
- List.map (fun { cbname } -> cbname) closures @ ["user_data"]
+| Closure (_, { cbname }) -> [cbname; sprintf "%s_user_data"
cbname ]
| Flags n -> [n]
| Int n -> [n]
| Int64 n -> [n]
@@ -3241,19 +3228,16 @@ let rec print_arg_list ?(handle = false) ?(user_data =
false)
pr "%s, " n;
if types then pr "size_t ";
pr "%s" len
- | Closure (_, cls) ->
- List.iter (
- fun { cbname; cbargs } ->
- if types then (
- pr "int (*%s) " cbname;
- print_arg_list ~user_data:true cbargs;
- )
- else
- pr "%s" cbname;
- pr ", "
- ) cls;
+ | Closure (_, { cbname; cbargs }) ->
+ if types then (
+ pr "int (*%s) " cbname;
+ print_arg_list ~user_data:true cbargs;
+ )
+ else
+ pr "%s" cbname;
+ pr ", ";
if types then pr "void *";
- pr "user_data"
+ pr "%s_user_data" cbname
| Flags n ->
if types then pr "uint32_t ";
pr "%s" n
@@ -3811,154 +3795,140 @@ let print_python_binding name { args; ret } *)
List.iter (
function
- | Closure (persistent, cls) ->
- pr "struct %s_user_data {\n" name;
- List.iter (
- fun { cbname } ->
- pr " PyObject *%s;\n" cbname
- ) cls;
- pr "};\n";
- pr "\n";
-
+ | Closure (persistent, { cbname; cbargs }) ->
(* Persistent closures need an explicit function to decrement
* the closure refcounts and free the user_data struct.
*)
if persistent then (
pr "static void\n";
- pr "free_%s_user_data (void *vp)\n" name;
+ pr "free_%s_%s_user_data (void *vp)\n" name cbname;
pr "{\n";
- pr " struct %s_user_data *user_data = vp;\n" name;
+ pr " PyObject *user_data = vp;\n";
pr "\n";
- List.iter (
- fun { cbname } ->
- pr " Py_DECREF (user_data->%s);\n" cbname
- ) cls;
- pr " free (user_data);\n";
+ pr " Py_DECREF (user_data);\n";
pr "}\n";
pr "\n";
);
+ pr "/* Wrapper for %s callback of %s. */\n" cbname name;
+ pr "static int\n";
+ pr "%s_%s_wrapper " name cbname;
+ C.print_arg_list ~user_data:true cbargs;
+ pr "\n";
+ pr "{\n";
+ pr " int ret;\n";
+ pr " PyGILState_STATE py_save = PyGILState_UNLOCKED;\n";
+ pr " PyObject *py_args, *py_ret;\n";
List.iter (
- fun { cbname; cbargs } ->
- pr "static int\n";
- pr "%s_%s_wrapper " name cbname;
- C.print_arg_list ~user_data:true cbargs;
- pr "\n";
- pr "{\n";
- pr " int ret;\n";
- pr " PyGILState_STATE py_save = PyGILState_UNLOCKED;\n";
- pr " PyObject *py_args, *py_ret;\n";
- List.iter (
- function
- | ArrayAndLen (UInt32 n, len) ->
- pr " PyObject *py_%s = PyList_New (%s);\n" n len;
- pr " for (size_t i = 0; i < %s; ++i)\n" len;
- pr " PyList_SET_ITEM (py_%s, i, PyLong_FromUnsignedLong
(%s[i]));\n" n n
- | BytesIn _
- | Int _
- | Int64 _ -> ()
- | Mutable (Int n) ->
- pr " PyObject *py_%s_modname = PyUnicode_FromString
(\"ctypes\");\n" n;
- pr " if (!py_%s_modname) { PyErr_PrintEx (0); return -1;
}\n" n;
- pr " PyObject *py_%s_mod = PyImport_Import
(py_%s_modname);\n" n n;
- pr " Py_DECREF (py_%s_modname);\n" n;
- pr " if (!py_%s_mod) { PyErr_PrintEx (0); return -1;
}\n" n;
- pr " PyObject *py_%s = PyObject_CallMethod (py_%s_mod,
\"c_int\", \"i\", *%s);\n" n n n;
- pr " if (!py_%s) { PyErr_PrintEx (0); return -1;
}\n" n;
- | String n
- | UInt64 n -> ()
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
- pr "\n";
+ function
+ | ArrayAndLen (UInt32 n, len) ->
+ pr " PyObject *py_%s = PyList_New (%s);\n" n len;
+ pr " for (size_t i = 0; i < %s; ++i)\n" len;
+ pr " PyList_SET_ITEM (py_%s, i, PyLong_FromUnsignedLong
(%s[i]));\n" n n
+ | BytesIn _
+ | Int _
+ | Int64 _ -> ()
+ | Mutable (Int n) ->
+ pr " PyObject *py_%s_modname = PyUnicode_FromString
(\"ctypes\");\n" n;
+ pr " if (!py_%s_modname) { PyErr_PrintEx (0); return -1;
}\n" n;
+ pr " PyObject *py_%s_mod = PyImport_Import
(py_%s_modname);\n" n n;
+ pr " Py_DECREF (py_%s_modname);\n" n;
+ pr " if (!py_%s_mod) { PyErr_PrintEx (0); return -1;
}\n" n;
+ pr " PyObject *py_%s = PyObject_CallMethod (py_%s_mod,
\"c_int\", \"i\", *%s);\n" n n n;
+ pr " if (!py_%s) { PyErr_PrintEx (0); return -1; }\n" n;
+ | String n
+ | UInt64 n -> ()
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
+ pr "\n";
- pr " py_args = Py_BuildValue (\"(\"";
- List.iter (
- function
- | ArrayAndLen (UInt32 n, len) -> pr "
\"O\""
- | BytesIn (n, len) -> pr " \"y#\""
- | Int n -> pr " \"i\""
- | Int64 n -> pr " \"L\""
- | Mutable (Int n) -> pr " \"O\""
- | String n -> pr " \"s\""
- | UInt64 n -> pr " \"K\""
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
- pr " \")\"";
- List.iter (
- function
- | ArrayAndLen (UInt32 n, _) -> pr ", py_%s" n
- | BytesIn (n, len) -> pr ", %s, (int) %s" n len
- | Mutable (Int n) -> pr ", py_%s" n
- | Int n | Int64 n
- | String n
- | UInt64 n -> pr ", %s" n
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
- pr ");\n";
- pr " Py_INCREF (py_args);\n";
- pr "\n";
- pr " if (PyEval_ThreadsInitialized ())\n";
- pr " py_save = PyGILState_Ensure ();\n";
- pr "\n";
- pr " py_ret = PyObject_CallObject (((struct %s_user_data
*)user_data)->%s, py_args);\n" name cbname;
- pr "\n";
- pr " if (PyEval_ThreadsInitialized ())\n";
- pr " PyGILState_Release (py_save);\n";
- pr "\n";
- pr " Py_DECREF (py_args);\n";
- pr "\n";
- pr " if (py_ret != NULL) {\n";
- pr " ret = 0;\n";
- pr " Py_DECREF (py_ret); /* return value is discarded
*/\n";
- pr " }\n";
- pr " else {\n";
- pr " ret = -1;\n";
- pr " PyErr_PrintEx (0); /* print exception */\n";
- pr " };\n";
- pr "\n";
- List.iter (
- function
- | ArrayAndLen (UInt32 n, _) ->
- pr " Py_DECREF (py_%s);\n" n
- | Mutable (Int n) ->
- pr " PyObject *py_%s_ret = PyObject_GetAttrString (py_%s,
\"value\");\n" n n;
- pr " *%s = PyLong_AsLong (py_%s_ret);\n" n n;
- pr " Py_DECREF (py_%s_ret);\n" n;
- pr " Py_DECREF (py_%s);\n" n
- | BytesIn _
- | Int _ | Int64 _
- | String _
- | UInt64 _ -> ()
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
- pr " return ret;\n";
- pr "}\n";
- pr "\n"
- ) cls
+ pr " py_args = Py_BuildValue (\"(\"";
+ List.iter (
+ function
+ | ArrayAndLen (UInt32 n, len) -> pr " \"O\""
+ | BytesIn (n, len) -> pr " \"y#\""
+ | Int n -> pr " \"i\""
+ | Int64 n -> pr " \"L\""
+ | Mutable (Int n) -> pr " \"O\""
+ | String n -> pr " \"s\""
+ | UInt64 n -> pr " \"K\""
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
+ pr " \")\"";
+ List.iter (
+ function
+ | ArrayAndLen (UInt32 n, _) -> pr ", py_%s" n
+ | BytesIn (n, len) -> pr ", %s, (int) %s" n len
+ | Mutable (Int n) -> pr ", py_%s" n
+ | Int n | Int64 n
+ | String n
+ | UInt64 n -> pr ", %s" n
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
+ pr ");\n";
+ pr " Py_INCREF (py_args);\n";
+ pr "\n";
+ pr " if (PyEval_ThreadsInitialized ())\n";
+ pr " py_save = PyGILState_Ensure ();\n";
+ pr "\n";
+ pr " py_ret = PyObject_CallObject ((PyObject *)user_data,
py_args);\n";
+ pr "\n";
+ pr " if (PyEval_ThreadsInitialized ())\n";
+ pr " PyGILState_Release (py_save);\n";
+ pr "\n";
+ pr " Py_DECREF (py_args);\n";
+ pr "\n";
+ pr " if (py_ret != NULL) {\n";
+ pr " ret = 0;\n";
+ pr " Py_DECREF (py_ret); /* return value is discarded
*/\n";
+ pr " }\n";
+ pr " else {\n";
+ pr " ret = -1;\n";
+ pr " PyErr_PrintEx (0); /* print exception */\n";
+ pr " };\n";
+ pr "\n";
+ List.iter (
+ function
+ | ArrayAndLen (UInt32 n, _) ->
+ pr " Py_DECREF (py_%s);\n" n
+ | Mutable (Int n) ->
+ pr " PyObject *py_%s_ret = PyObject_GetAttrString (py_%s,
\"value\");\n" n n;
+ pr " *%s = PyLong_AsLong (py_%s_ret);\n" n n;
+ pr " Py_DECREF (py_%s_ret);\n" n;
+ pr " Py_DECREF (py_%s);\n" n
+ | BytesIn _
+ | Int _ | Int64 _
+ | String _
+ | UInt64 _ -> ()
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
+ pr " return ret;\n";
+ pr "}\n";
+ pr "\n"
| _ -> ()
) args;
@@ -3996,11 +3966,8 @@ let print_python_binding name { args; ret } pr
" PyObject *%s; /* PyCapsule pointing to struct py_aio_buffer */\n"
n;
pr " struct py_aio_buffer *%s_buf;\n" n
- | Closure (false, cls) ->
- pr " struct %s_user_data _user_data;\n" name;
- pr " struct %s_user_data *user_data = &_user_data;\n"
name
- | Closure (true, cls) ->
- pr " struct %s_user_data *user_data;\n" name
+ | Closure (_, { cbname }) ->
+ pr " PyObject *%s_user_data;\n" cbname
| Flags n ->
pr " uint32_t %s_u32;\n" n;
pr " unsigned int %s; /* really uint32_t */\n" n
@@ -4031,19 +3998,6 @@ let print_python_binding name { args; ret } ) args;
pr "\n";
- (* Allocate the persistent closure user_data. *)
- List.iter (
- function
- | Closure (false, _) -> ()
- | Closure (true, cls) ->
- pr " user_data = malloc (sizeof *user_data);\n";
- pr " if (user_data == NULL) {\n";
- pr " PyErr_NoMemory ();\n";
- pr " return NULL;\n";
- pr " }\n"
- | _ -> ()
- ) args;
-
(* Parse the Python parameters. *)
pr " if (!PyArg_ParseTuple (args, (char *) \"O\"";
List.iter (
@@ -4054,7 +4008,7 @@ let print_python_binding name { args; ret } |
BytesPersistIn (n, _) -> pr " \"O\""
| BytesOut (_, count) -> pr " \"n\""
| BytesPersistOut (_, count) -> pr " \"O\""
- | Closure (_, cls) -> List.iter (fun _ -> pr "
\"O\"") cls
+ | Closure _ -> pr " \"O\""
| Flags n -> pr " \"I\""
| Int n -> pr " \"i\""
| Int64 n -> pr " \"L\""
@@ -4078,8 +4032,7 @@ let print_python_binding name { args; ret } | BytesIn
(n, _) | BytesPersistIn (n, _)
| BytesPersistOut (n, _) -> pr ", &%s" n
| BytesOut (_, count) -> pr ", &%s" count
- | Closure (_, cls) ->
- List.iter (fun { cbname } -> pr ", &user_data->%s"
cbname) cls
+ | Closure (_, { cbname }) -> pr ", &%s_user_data" cbname
| Flags n -> pr ", &%s" n
| Int n -> pr ", &%s" n
| Int64 n -> pr ", &%s" n
@@ -4101,11 +4054,8 @@ let print_python_binding name { args; ret } List.iter
(
function
| Closure (false, _) -> ()
- | Closure (true, cls) ->
- List.iter (
- fun { cbname } ->
- pr " Py_INCREF (user_data->%s);\n" cbname
- ) cls
+ | Closure (true, { cbname }) ->
+ pr " Py_INCREF (%s_user_data);\n" cbname
| _ -> ()
) args;
@@ -4136,15 +4086,12 @@ let print_python_binding name { args; ret } pr
" %s = malloc (%s);\n" n count
| BytesPersistIn (n, _) | BytesPersistOut (n, _) ->
pr " %s_buf = nbd_internal_py_get_aio_buffer (%s);\n" n n
- | Closure (_, cls) ->
- List.iter (
- fun { cbname } ->
- pr " if (!PyCallable_Check (user_data->%s)) {\n"
cbname;
- pr " PyErr_SetString (PyExc_TypeError,\n";
- pr " \"callback parameter %s is not
callable\");\n" cbname;
- pr " return NULL;\n";
- pr " }\n"
- ) cls
+ | Closure (_, { cbname }) ->
+ pr " if (!PyCallable_Check (%s_user_data)) {\n" cbname;
+ pr " PyErr_SetString (PyExc_TypeError,\n";
+ pr " \"callback parameter %s is not
callable\");\n" cbname;
+ pr " return NULL;\n";
+ pr " }\n"
| Flags n -> pr " %s_u32 = %s;\n" n n
| Int _ -> ()
| Int64 n -> pr " %s_i64 = %s;\n" n n
@@ -4175,12 +4122,9 @@ let print_python_binding name { args; ret } |
BytesOut (n, count) -> pr ", %s, %s" n count
| BytesPersistIn (n, _)
| BytesPersistOut (n, _) -> pr ", %s_buf->data,
%s_buf->len" n n
- | Closure (_, cls) ->
- List.iter (
- fun { cbname } ->
- pr ", %s_%s_wrapper" name cbname
- ) cls;
- pr ", user_data"
+ | Closure (_, { cbname }) ->
+ pr ", %s_%s_wrapper" name cbname;
+ pr ", %s_user_data" cbname
| Flags n -> pr ", %s_u32" n
| Int n -> pr ", %s" n
| Int64 n -> pr ", %s_i64" n
@@ -4257,9 +4201,10 @@ let print_python_binding name { args; ret } |
BytesIn (n, _) -> pr " PyBuffer_Release (&%s);\n" n
| BytesPersistIn _ | BytesOut _ | BytesPersistOut _ -> ()
| Closure (false, _) -> ()
- | Closure (true, _) ->
+ | Closure (true, { cbname }) ->
pr " /* This ensures the callback data is freed eventually.
*/\n";
- pr " nbd_add_close_callback (h, free_%s_user_data,
user_data);\n" name
+ pr " nbd_add_close_callback (h, free_%s_%s_user_data,
%s_user_data);\n"
+ name cbname cbname
| Flags _ -> ()
| Int _ -> ()
| Int64 _ -> ()
@@ -4406,8 +4351,7 @@ class NBD (object):
| BytesIn (n, _) | BytesPersistIn (n, _) -> [n, None]
| BytesPersistOut (n, _) -> [n, None]
| BytesOut (_, count) -> [count, None]
- | Closure (_, cls) ->
- List.map (fun { cbname } -> cbname, None) cls
+ | Closure (_, { cbname }) -> [cbname, None]
| Flags n -> [n, Some "0"]
| Int n -> [n, None]
| Int64 n -> [n, None]
@@ -4471,7 +4415,6 @@ end = struct
type ocaml_arg | OCamlHandle (* The NBD handle (NBD.t) *)
| OCamlFlags of string (* Optional ?flags parameter *)
- | OCamlClosure of bool * closure (* Single closure parameter *)
| OCamlArg of arg (* Other arg (string = name). *)
let args_to_ocaml_args args @@ -4483,8 +4426,6 @@ let args_to_ocaml_args args
let args List.map (
function
- | Closure (persistent, cls) ->
- List.map (fun cl -> OCamlClosure (persistent, cl)) cls
| a -> [OCamlArg a]
) args in
let args = List.flatten args in
@@ -4502,10 +4443,6 @@ let rec ocaml_fundecl_to_string args ret and
ocaml_arg_to_string = function
| OCamlHandle -> "t"
| OCamlFlags n -> sprintf "?%s:int32 list" n
- | OCamlClosure (_, { cbargs }) ->
- sprintf "(%s)"
- (ocaml_fundecl_to_string (List.map (fun a -> OCamlArg a)
cbargs)
- RErr)
| OCamlArg (ArrayAndLen (t, _)) ->
sprintf "%s array" (ocaml_arg_to_string (OCamlArg t))
| OCamlArg (Bool _) -> "bool"
@@ -4513,7 +4450,10 @@ and ocaml_arg_to_string = function
| OCamlArg (BytesPersistIn _) -> "Buffer.t"
| OCamlArg (BytesOut _) -> "bytes"
| OCamlArg (BytesPersistOut _) -> "Buffer.t"
- | OCamlArg (Closure _) -> assert false (* see above *)
+ | OCamlArg (Closure (_, { cbargs })) ->
+ sprintf "(%s)"
+ (ocaml_fundecl_to_string (List.map (fun a -> OCamlArg a)
cbargs)
+ RErr)
| OCamlArg (Flags _) -> assert false (* see above *)
| OCamlArg (Int _) -> "int"
| OCamlArg (Int64 _) -> "int64"
@@ -4538,7 +4478,6 @@ and ocaml_ret_to_string = function
let rec name_of_ocaml_arg = function
| OCamlHandle -> "h"
| OCamlFlags n -> n
- | OCamlClosure (_, { cbname }) -> cbname
| OCamlArg a ->
match a with
| ArrayAndLen (arg, n) -> name_of_ocaml_arg (OCamlArg arg)
@@ -4547,7 +4486,7 @@ let rec name_of_ocaml_arg = function
| BytesOut (n, len) -> n
| BytesPersistIn (n, len) -> n
| BytesPersistOut (n, len) -> n
- | Closure (_, closures) -> assert false
+ | Closure (_, { cbname }) -> cbname
| Flags n -> n
| Int n -> n
| Int64 n -> n
@@ -4705,42 +4644,31 @@ let print_ocaml_binding (name, { args; ret }) (*
Functions with a callback parameter require special handling. *)
List.iter (
function
- | Closure (persistent, cls) ->
- pr "struct %s_user_data {\n" name;
- List.iter (fun { cbname } -> pr " value %s;\n" cbname)
cls;
- pr "};\n";
- pr "\n";
-
+ | Closure (persistent, { cbname; cbargs }) ->
(* Persistent closures need an explicit function to remove
* the global root and free the user_data struct.
*)
if persistent then (
pr "static void\n";
- pr "free_%s_user_data (void *vp)\n" name;
+ pr "free_%s_%s_user_data (void *vp)\n" name cbname;
pr "{\n";
- pr " struct %s_user_data *user_data = vp;\n" name;
+ pr " value *user_data = vp;\n";
pr "\n";
- List.iter (
- fun { cbname } ->
- pr " caml_remove_generational_global_root
(&user_data->%s);\n"
- cbname
- ) cls;
+ pr " caml_remove_generational_global_root (user_data);\n";
pr " free (user_data);\n";
pr "}\n";
pr "\n"
);
- List.iter (
- fun { cbname; cbargs } ->
- let argnames - List.map (
- function
- | ArrayAndLen (UInt32 n, _) | BytesIn (n, _)
+ let argnames + List.map (
+ function
+ | ArrayAndLen (UInt32 n, _) | BytesIn (n, _)
| Int n | Int64 n
| Mutable (Int n) | String n | UInt64 n ->
- n ^ "v"
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
+ n ^ "v"
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
| BytesPersistIn _ | BytesPersistOut _
| Closure _
| Flags _ | Path _ | Mutable _
@@ -4748,105 +4676,105 @@ let print_ocaml_binding (name, { args; ret })
| UInt _ | UInt32 _ -> assert false
) cbargs in
- pr "static int\n";
- pr "%s_%s_wrapper_locked " name cbname;
- C.print_arg_list ~user_data:true cbargs;
- pr "\n";
- pr "{\n";
- pr " CAMLparam0 ();\n";
- assert (List.length argnames <= 5);
- pr " CAMLlocal%d (%s);\n" (List.length argnames)
- (String.concat ", " argnames);
- pr " CAMLlocal2 (fnv, rv);\n";
- pr " value args[%d];\n" (List.length argnames);
- pr "\n";
+ pr "/* Wrapper for %s callback of %s. */\n" cbname name;
+ pr "static int\n";
+ pr "%s_%s_wrapper_locked " name cbname;
+ C.print_arg_list ~user_data:true cbargs;
+ pr "\n";
+ pr "{\n";
+ pr " CAMLparam0 ();\n";
+ assert (List.length argnames <= 5);
+ pr " CAMLlocal%d (%s);\n" (List.length argnames)
+ (String.concat ", " argnames);
+ pr " CAMLlocal2 (fnv, rv);\n";
+ pr " value args[%d];\n" (List.length argnames);
+ pr "\n";
- List.iter (
- function
- | ArrayAndLen (UInt32 n, count) ->
- pr " %sv = nbd_internal_ocaml_alloc_int32_array (%s,
%s);\n"
- n n count;
- | BytesIn (n, len) ->
- pr " %sv = caml_alloc_string (%s);\n" n len;
- pr " memcpy (String_val (%sv), %s, %s);\n" n n len
- | Int n ->
- pr " %sv = Val_int (%s);\n" n n
- | Int64 n ->
- pr " %sv = caml_copy_int64 (%s);\n" n n
- | String n ->
- pr " %sv = caml_copy_string (%s);\n" n n
- | UInt64 n ->
- pr " %sv = caml_copy_int64 (%s);\n" n n
- | Mutable (Int n) ->
- pr " %sv = caml_alloc_tuple (1);\n" n;
- pr " Store_field (%sv, 0, Val_int (*%s));\n" n n
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
+ List.iter (
+ function
+ | ArrayAndLen (UInt32 n, count) ->
+ pr " %sv = nbd_internal_ocaml_alloc_int32_array (%s,
%s);\n"
+ n n count;
+ | BytesIn (n, len) ->
+ pr " %sv = caml_alloc_string (%s);\n" n len;
+ pr " memcpy (String_val (%sv), %s, %s);\n" n n len
+ | Int n ->
+ pr " %sv = Val_int (%s);\n" n n
+ | Int64 n ->
+ pr " %sv = caml_copy_int64 (%s);\n" n n
+ | String n ->
+ pr " %sv = caml_copy_string (%s);\n" n n
+ | UInt64 n ->
+ pr " %sv = caml_copy_int64 (%s);\n" n n
+ | Mutable (Int n) ->
+ pr " %sv = caml_alloc_tuple (1);\n" n;
+ pr " Store_field (%sv, 0, Val_int (*%s));\n" n n
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
- List.iteri (fun i n -> pr " args[%d] = %s;\n" i n)
argnames;
+ List.iteri (fun i n -> pr " args[%d] = %s;\n" i n)
argnames;
- pr " fnv = ((struct %s_user_data *)user_data)->%s;\n"
name cbname;
+ pr " fnv = * (value *) user_data;\n";
- pr " rv = caml_callbackN_exn (fnv, %d, args);\n"
- (List.length argnames);
+ pr " rv = caml_callbackN_exn (fnv, %d, args);\n"
+ (List.length argnames);
- List.iter (
- function
- | ArrayAndLen (UInt32 n, count) -> ()
- | BytesIn (n, len) -> ()
- | Int n -> ()
- | Int64 n -> ()
- | String n -> ()
- | UInt64 n -> ()
- | Mutable (Int n) ->
- pr " *%s = Int_val (Field (%sv, 0));\n" n n
- (* The following not yet implemented for callbacks XXX *)
- | ArrayAndLen _ | Bool _ | BytesOut _
- | BytesPersistIn _ | BytesPersistOut _
- | Closure _
- | Flags _ | Mutable _
- | Path _ | SockAddrAndLen _ | StringList _
- | UInt _ | UInt32 _ -> assert false
- ) cbargs;
+ List.iter (
+ function
+ | ArrayAndLen (UInt32 n, count) -> ()
+ | BytesIn (n, len) -> ()
+ | Int n -> ()
+ | Int64 n -> ()
+ | String n -> ()
+ | UInt64 n -> ()
+ | Mutable (Int n) ->
+ pr " *%s = Int_val (Field (%sv, 0));\n" n n
+ (* The following not yet implemented for callbacks XXX *)
+ | ArrayAndLen _ | Bool _ | BytesOut _
+ | BytesPersistIn _ | BytesPersistOut _
+ | Closure _
+ | Flags _ | Mutable _
+ | Path _ | SockAddrAndLen _ | StringList _
+ | UInt _ | UInt32 _ -> assert false
+ ) cbargs;
- pr " if (Is_exception_result (rv)) {\n";
- pr " /* XXX This is not really an error as callbacks can
return\n";
- pr " * an error indication. But perhaps we should direct
this\n";
- pr " * to a more suitable place or formalize what
exception\n";
- pr " * means error versus unexpected failure.\n";
- pr " */\n";
- pr " fprintf (stderr,\n";
- pr " \"libnbd: uncaught OCaml exception:
%%s\\n\",\n";
- pr " caml_format_exception (Extract_exception
(rv)));\n";
- pr " CAMLreturnT (int, -1);\n";
- pr " }\n";
+ pr " if (Is_exception_result (rv)) {\n";
+ pr " /* XXX This is not really an error as callbacks can
return\n";
+ pr " * an error indication. But perhaps we should direct
this\n";
+ pr " * to a more suitable place or formalize what
exception\n";
+ pr " * means error versus unexpected failure.\n";
+ pr " */\n";
+ pr " fprintf (stderr,\n";
+ pr " \"libnbd: uncaught OCaml exception:
%%s\\n\",\n";
+ pr " caml_format_exception (Extract_exception
(rv)));\n";
+ pr " CAMLreturnT (int, -1);\n";
+ pr " }\n";
- pr "\n";
- pr " CAMLreturnT (int, 0);\n";
- pr "}\n";
- pr "\n";
- pr "static int\n";
- pr "%s_%s_wrapper " name cbname;
- C.print_arg_list ~user_data:true cbargs;
- pr "\n";
- pr "{\n";
- pr " int ret;\n";
- pr "\n";
- pr " caml_leave_blocking_section ();\n";
- pr " ret = %s_%s_wrapper_locked " name cbname;
- C.print_arg_list ~user_data:true ~types:false cbargs;
- pr ";\n";
- pr " caml_enter_blocking_section ();\n";
- pr " return ret;\n";
- pr "}\n";
- pr "\n"
- ) cls
+ pr "\n";
+ pr " CAMLreturnT (int, 0);\n";
+ pr "}\n";
+ pr "\n";
+ pr "static int\n";
+ pr "%s_%s_wrapper " name cbname;
+ C.print_arg_list ~user_data:true cbargs;
+ pr "\n";
+ pr "{\n";
+ pr " int ret;\n";
+ pr "\n";
+ pr " caml_leave_blocking_section ();\n";
+ pr " ret = %s_%s_wrapper_locked " name cbname;
+ C.print_arg_list ~user_data:true ~types:false cbargs;
+ pr ";\n";
+ pr " caml_enter_blocking_section ();\n";
+ pr " return ret;\n";
+ pr "}\n";
+ pr "\n"
| _ -> ()
) args;
@@ -4889,32 +4817,6 @@ let print_ocaml_binding (name, { args; ret }) pr
" CAMLlocal1 (rv);\n";
pr "\n";
- (* Set up user_data for closures. *)
- let has_closures - try
- let cl = List.find (function Closure _ -> true | _ -> false) args
in
- match cl with
- | Closure (b, _) -> Some b
- | _ -> assert false
- with
- Not_found -> None in
- (match has_closures with
- | None -> ()
- | Some false ->
- pr " /* This is safe because we only call this while this
stack\n";
- pr " * frame is live.\n";
- pr " */\n";
- pr " struct %s_user_data _user_data;\n" name;
- pr " struct %s_user_data *user_data = &_user_data;\n"
name
- | Some true ->
- pr " /* The function may save a reference to the closure, so
we\n";
- pr " * must treat it as a possible GC root.\n";
- pr " */\n";
- pr " struct %s_user_data *user_data;\n" name;
- pr " user_data = malloc (sizeof *user_data);\n";
- pr " if (user_data == NULL) caml_raise_out_of_memory ();\n"
- );
-
List.iter (
function
| OCamlHandle ->
@@ -4927,14 +4829,6 @@ let print_ocaml_binding (name, { args; ret }) pr
" %s = Flags_val (Field (%sv, 0));\n" n n;
pr " else /* None */\n";
pr " %s = 0;\n" n
- | OCamlClosure (false, { cbname }) ->
- pr " user_data->%s = %sv;\n" cbname cbname;
- pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname
- | OCamlClosure (true, { cbname }) ->
- pr " user_data->%s = %sv;\n" cbname cbname;
- pr " caml_register_generational_global_root
(&user_data->%s);\n"
- cbname;
- pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname
| OCamlArg (ArrayAndLen (t, _)) -> (* XXX *) ()
| OCamlArg (Bool n) ->
pr " bool %s = Bool_val (%sv);\n" n n
@@ -4952,7 +4846,26 @@ let print_ocaml_binding (name, { args; ret }) pr
" struct nbd_buffer %s_buf = NBD_buffer_val (%sv);\n" n n;
pr " void *%s = %s_buf.data;\n" n n;
pr " size_t %s = %s_buf.len;\n" count n
- | OCamlArg (Closure _) -> assert false (* see above *)
+ | OCamlArg (Closure (false, { cbname })) ->
+ pr " /* This is safe because we only call this while this
stack\n";
+ pr " * frame is live.\n";
+ pr " */\n";
+ pr " CAMLlocal1 (_%s_user_data);\n" cbname;
+ pr " value *%s_user_data = &_%s_user_data;\n" cbname
cbname;
+ pr " _%s_user_data = %sv;\n" cbname cbname;
+ pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname
+ | OCamlArg (Closure (true, { cbname })) ->
+ pr " /* The function may save a reference to the closure, so
we\n";
+ pr " * must treat it as a possible GC root.\n";
+ pr " */\n";
+ pr " value *%s_user_data;\n" cbname;
+ pr " %s_user_data = malloc (sizeof (value));\n" cbname;
+ pr " if (%s_user_data == NULL) caml_raise_out_of_memory
();\n" cbname;
+ pr " caml_register_generational_global_root
(%s_user_data);\n" cbname;
+ pr " *%s_user_data = %sv;\n" cbname cbname;
+ pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname;
+ pr " nbd_add_close_callback (h, free_%s_%s_user_data,
%s_user_data);\n"
+ name cbname cbname
| OCamlArg (Flags _) -> assert false (* see above *)
| OCamlArg (Int n) ->
pr " int %s = Int_val (%sv);\n" n n
@@ -4975,12 +4888,6 @@ let print_ocaml_binding (name, { args; ret }) pr
" uint64_t %s = Int64_val (%sv);\n" n n
) oargs;
- (match has_closures with
- | None | Some false -> ()
- | Some true ->
- pr " nbd_add_close_callback (h, free_%s_user_data,
user_data);\n" name
- );
-
let errcode match ret with
| RBool | RErr | RFd | RInt | RInt64 -> pr " int r;\n";
"-1"
@@ -5014,7 +4921,6 @@ let print_ocaml_binding (name, { args; ret }) |
OCamlArg (StringList n) -> pr " free (%s);\n" n
| OCamlHandle
| OCamlFlags _
- | OCamlClosure _
| OCamlArg (ArrayAndLen _)
| OCamlArg (Bool _)
| OCamlArg (BytesIn _)
diff --git a/generator/states-reply-simple.c b/generator/states-reply-simple.c
index f1770fc..94875aa 100644
--- a/generator/states-reply-simple.c
+++ b/generator/states-reply-simple.c
@@ -64,7 +64,7 @@
int error = 0;
assert (cmd->error == 0);
- if (cmd->cb.fn.read (cmd->cb.user_data, cmd->data,
cmd->count,
+ if (cmd->cb.fn.read (cmd->cb.fn_user_data, cmd->data,
cmd->count,
cmd->offset, LIBNBD_READ_DATA, &error) == -1)
cmd->error = error ? error : EPROTO;
}
diff --git a/generator/states-reply-structured.c
b/generator/states-reply-structured.c
index 25987ed..f60232e 100644
--- a/generator/states-reply-structured.c
+++ b/generator/states-reply-structured.c
@@ -298,7 +298,7 @@
* current error rather than any earlier one. If the callback fails
* without setting errno, then use the server's error below.
*/
- if (cmd->cb.fn.read (cmd->cb.user_data,
+ if (cmd->cb.fn.read (cmd->cb.fn_user_data,
cmd->data + (offset - cmd->offset),
0, offset, LIBNBD_READ_ERROR, &scratch) == -1)
if (cmd->error == 0)
@@ -385,7 +385,7 @@
if (cmd->cb.fn.read) {
int error = cmd->error;
- if (cmd->cb.fn.read (cmd->cb.user_data,
+ if (cmd->cb.fn.read (cmd->cb.fn_user_data,
cmd->data + (offset - cmd->offset),
length - sizeof offset, offset,
LIBNBD_READ_DATA, &error) == -1)
@@ -447,7 +447,7 @@
if (cmd->cb.fn.read) {
int error = cmd->error;
- if (cmd->cb.fn.read (cmd->cb.user_data,
+ if (cmd->cb.fn.read (cmd->cb.fn_user_data,
cmd->data + offset, length,
cmd->offset + offset,
LIBNBD_READ_HOLE, &error) == -1)
@@ -499,7 +499,7 @@
/* Call the caller's extent function. */
int error = cmd->error;
- if (cmd->cb.fn.extent (cmd->cb.user_data,
+ if (cmd->cb.fn.extent (cmd->cb.fn_user_data,
meta_context->name, cmd->offset,
&h->bs_entries[1], (length-4) / 4,
&error) == -1)
if (cmd->error == 0)
diff --git a/lib/internal.h b/lib/internal.h
index 3f2d3f8..b2a65bc 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -269,8 +269,9 @@ struct command_cb {
extent_fn extent;
read_fn read;
} fn;
+ void *fn_user_data; /* associated with one of the fn callbacks above */
callback_fn callback;
- void *user_data;
+ void *user_data; /* associated with the callback function */
};
struct command {
diff --git a/lib/rw.c b/lib/rw.c
index 680b81a..7999a86 100644
--- a/lib/rw.c
+++ b/lib/rw.c
@@ -280,18 +280,24 @@ nbd_unlocked_aio_pread_structured (struct nbd_handle *h,
void *buf,
uint32_t flags)
{
return nbd_unlocked_aio_pread_structured_callback (h, buf, count, offset,
- read, NULL, user_data,
+ read, user_data,
+ NULL, NULL,
flags);
}
int64_t
nbd_unlocked_aio_pread_structured_callback (struct nbd_handle *h, void *buf,
size_t count, uint64_t offset,
- read_fn read, callback_fn callback,
- void *user_data, uint32_t flags)
+ read_fn read,
+ void *read_user_data,
+ callback_fn callback,
+ void *callback_user_data,
+ uint32_t flags)
{
- struct command_cb cb = { .fn.read = read, .callback = callback,
- .user_data = user_data, };
+ struct command_cb cb = { .fn.read = read,
+ .fn_user_data = read_user_data,
+ .callback = callback,
+ .user_data = callback_user_data, };
if ((flags & ~LIBNBD_CMD_FLAG_DF) != 0) {
set_error (EINVAL, "invalid flag: %" PRIu32, flags);
@@ -493,18 +499,24 @@ nbd_unlocked_aio_block_status (struct nbd_handle *h,
uint32_t flags)
{
return nbd_unlocked_aio_block_status_callback (h, count, offset,
- extent, NULL, user_data,
+ extent, user_data,
+ NULL, NULL,
flags);
}
int64_t
nbd_unlocked_aio_block_status_callback (struct nbd_handle *h,
uint64_t count, uint64_t offset,
- extent_fn extent, callback_fn callback,
- void *user_data, uint32_t flags)
+ extent_fn extent,
+ void *extent_user_data,
+ callback_fn callback,
+ void *callback_user_data,
+ uint32_t flags)
{
- struct command_cb cb = { .fn.extent = extent, .callback = callback,
- .user_data = user_data, };
+ struct command_cb cb = { .fn.extent = extent,
+ .fn_user_data = extent_user_data,
+ .callback = callback,
+ .user_data = callback_user_data };
if (!h->structured_replies) {
set_error (ENOTSUP, "server does not support structured
replies");
--
2.22.0
Richard W.M. Jones
2019-Jul-24 12:17 UTC
[Libguestfs] [PATCH libnbd 2/3] lib: Implement closure lifetimes.
Previously closures had a crude flag which tells if they are
persistent or transient. Transient closures (flag = false) last for
the lifetime of the currently called libnbd function. Persistent
closures had an indefinite lifetime which could last for as long as
the handle. In language bindings handling persistent closures was
wasteful as we needed to register a "close callback" to free the
closure when the handle is closed. But if you had submitted thousands
of asynchronous commands you would end up registering thousands of
close callbacks.
We actually have far more information about the lifetime of closures.
We know precisely when they will no longer be needed by the library.
Callers can use this information to free up associated user data
earlier. In particular in language bindings we can remove roots /
decrement reference counts at the right place to free the closure,
without waiting for the handle to be closed.
The solution to this is to introduce the concept of a closure
lifetime. The callback is called with an extra valid_flag parameter
which is a bitmap containing LIBNBD_CALLBACK_VALID and/or
LIBNBD_CALLBACK_FREE. LIBNBD_CALLBACK_VALID corresponds to a normal
call of the callback function by the library. After the library has
finished with the callback (declaring that this callback will never be
needed or called again), it is called once more with
valid_flag == LIBNBD_CALLBACK_FREE.
(Note it is also possible for the library to call the callback with
valid_flag == LIBNBD_CALLBACK_VALID|LIBNBD_CALLBACK_FREE, meaning it's the
last valid call.)
As an example, nbd_set_debug_callback registers a debug closure which
is saved in the handle. The closure is freed either when
nbd_set_debug_callback is called again, or the handle is closed. The
sequence of events would look like this:
Caller Callback
nbd_set_debug_callback
# a new debug_fn is registered
calls any nbd function debug_fn (valid_flag == VALID)
debug_fn (valid_flag == VALID)
debug_fn (valid_flag == VALID)
...
nbd_set_debug_callback
# the old debug_fn is freed
debug_fn (valid_flag == FREE)
# the new debug_fn is called
calls any nbd function debug_fn (valid_flag == VALID)
debug_fn (valid_flag == VALID)
# the second debug_fn is freed
nbd_close debug_fn (valid_flag == FREE)
An example of a debug_fn written by a caller would be:
int my_debug_fn (int valid_flag, void *user_data,
const char *context, const char *msg)
{
if (valid_flag & LIBNBD_CALLBACK_VALID) {
printf ("context = %s, msg = %s\n", context, msg);
}
if (valid_flag & LIBNBD_CALLBACK_FREE) {
/* If you need to free something, for example: */
free (user_data);
}
return 0;
}
---
docs/libnbd.pod | 54 ++++++-
examples/glib-main-loop.c | 16 +-
examples/strict-structured-reads.c | 11 +-
generator/generator | 243 ++++++++++++----------------
generator/states-reply-simple.c | 3 +-
generator/states-reply-structured.c | 8 +-
generator/states-reply.c | 3 +-
generator/states.c | 3 +-
interop/dirty-bitmap.c | 5 +-
interop/structured-read.c | 6 +-
lib/aio.c | 11 ++
lib/debug.c | 7 +-
lib/internal.h | 10 +-
tests/meta-base-allocation.c | 11 +-
tests/oldstyle.c | 10 +-
15 files changed, 233 insertions(+), 168 deletions(-)
diff --git a/docs/libnbd.pod b/docs/libnbd.pod
index 631bb3b..e9a6030 100644
--- a/docs/libnbd.pod
+++ b/docs/libnbd.pod
@@ -487,7 +487,59 @@ C<nbd_set_debug_callback>,
C<nbd_pread_callback>). Libnbd can call
these functions while processing.
Callbacks have an opaque C<void *user_data> pointer. This is passed
-as the first parameter to the callback.
+as the second parameter to the callback.
+
+=head2 Callback lifetimes
+
+All callbacks have an C<int valid_flag> parameter which is used to
+help with the lifetime of the callback. C<valid_flag> contains the
+I<logical or> of:
+
+=over 4
+
+=item C<LIBNBD_CALLBACK_VALID>
+
+The callback parameters are valid and this is a normal callback.
+
+=item C<LIBNBD_CALLBACK_FREE>
+
+This is the last time the library will call this function. Any data
+associated with the callback can be freed.
+
+=item other bits
+
+Other bits in C<valid_flag> should be ignored.
+
+=back
+
+For example C<nbd_set_debug_callback> sets up a callback which you
+could define like this:
+
+ int my_debug_fn (int valid_flag, void *user_data,
+ const char *context, const char *msg)
+ {
+ if (valid_flag & LIBNBD_CALLBACK_VALID) {
+ printf ("context = %s, msg = %s\n", context, msg);
+ }
+ if (valid_flag & LIBNBD_CALLBACK_FREE) {
+ /* If you need to free something, for example: */
+ free (user_data);
+ }
+ return 0;
+ }
+
+If you don't care about the freeing feature then it is also correct to
+write this:
+
+ int my_debug_fn (int valid_flag, void *user_data,
+ const char *context, const char *msg)
+ {
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID)) return 0;
+
+ // Rest of callback as normal.
+ }
+
+=head2 Callbacks and locking
The callbacks are invoked at a point where the libnbd lock is held; as
such, it is unsafe for the callback to call any C<nbd_*> APIs on the
diff --git a/examples/glib-main-loop.c b/examples/glib-main-loop.c
index c633c1d..9d61923 100644
--- a/examples/glib-main-loop.c
+++ b/examples/glib-main-loop.c
@@ -272,9 +272,11 @@ static GMainLoop *loop;
static void connected (struct NBDSource *source);
static gboolean read_data (gpointer user_data);
-static int finished_read (void *vp, int64_t rcookie, int *error);
+static int finished_read (int valid_flag, void *vp,
+ int64_t rcookie, int *error);
static gboolean write_data (gpointer user_data);
-static int finished_write (void *vp, int64_t wcookie, int *error);
+static int finished_write (int valid_flag, void *vp,
+ int64_t wcookie, int *error);
int
main (int argc, char *argv[])
@@ -395,10 +397,13 @@ read_data (gpointer user_data)
/* This callback is called from libnbd when any read command finishes. */
static int
-finished_read (void *vp, int64_t rcookie, int *error)
+finished_read (int valid_flag, void *vp, int64_t rcookie, int *error)
{
size_t i;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
if (gssrc == NULL)
return 0;
@@ -460,10 +465,13 @@ write_data (gpointer user_data)
/* This callback is called from libnbd when any write command finishes. */
static int
-finished_write (void *vp, int64_t wcookie, int *error)
+finished_write (int valid_flag, void *vp, int64_t wcookie, int *error)
{
size_t i;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
if (gsdest == NULL)
return 0;
diff --git a/examples/strict-structured-reads.c
b/examples/strict-structured-reads.c
index a50f662..c154b08 100644
--- a/examples/strict-structured-reads.c
+++ b/examples/strict-structured-reads.c
@@ -51,12 +51,16 @@ static int64_t total_bytes;
static int total_success;
static int
-read_chunk (void *opaque, const void *bufv, size_t count, uint64_t offset,
+read_chunk (int valid_flag, void *opaque,
+ const void *bufv, size_t count, uint64_t offset,
int status, int *error)
{
struct data *data = opaque;
struct range *r, **prev;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
/* libnbd guarantees this: */
assert (offset >= data->offset);
assert (offset + count <= data->offset + data->count);
@@ -127,11 +131,14 @@ read_chunk (void *opaque, const void *bufv, size_t count,
uint64_t offset,
}
static int
-read_verify (void *opaque, int64_t cookie, int *error)
+read_verify (int valid_flag, void *opaque, int64_t cookie, int *error)
{
struct data *data = opaque;
int ret = -1;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
total_reads++;
total_chunks += data->chunks;
if (*error)
diff --git a/generator/generator b/generator/generator
index 3b57713..5d5c267 100755
--- a/generator/generator
+++ b/generator/generator
@@ -849,10 +849,7 @@ and arg written by the
function *)
| BytesPersistIn of string * string (* same as above, but buffer persists *)
| BytesPersistOut of string * string
-| Closure of bool * closure (* function pointer + void *opaque
- flag if true means callbacks persist
- in the handle, false means they only
- exist during the function call *)
+| Closure of closure (* function pointer + void *opaque *)
| Flags of string (* NBD_CMD_FLAG_* flags *)
| Int of string (* small int *)
| Int64 of string (* 64 bit signed int *)
@@ -920,9 +917,8 @@ Return the state of the debug flag on this handle.";
"set_debug_callback", {
default_call with
- args = [ Closure (true,
- { cbname="debug_fn";
- cbargs=[String "context"; String
"msg"] }) ];
+ args = [ Closure { cbname="debug_fn";
+ cbargs=[String "context"; String
"msg"] } ];
ret = RErr;
shortdesc = "set the debug callback";
longdesc = "\
@@ -1350,11 +1346,10 @@ protocol extensions).";
"pread_structured", {
default_call with
args = [ BytesOut ("buf", "count"); UInt64
"offset";
- Closure (false,
- { cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset"; Int
"status";
- Mutable (Int "error")] });
+ Closure { cbname="chunk";
+ cbargs=[BytesIn ("subbuf", "count");
+ UInt64 "offset"; Int
"status";
+ Mutable (Int "error")] };
Flags "flags" ];
ret = RErr;
permitted_states = [ Connected ];
@@ -1541,13 +1536,12 @@ punching a hole.";
"block_status", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (false,
- { cbname="extent";
- cbargs=[String "metacontext";
- UInt64 "offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")]} );
+ Closure { cbname="extent";
+ cbargs=[String "metacontext";
+ UInt64 "offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")]};
Flags "flags" ];
ret = RErr;
permitted_states = [ Connected ];
@@ -1725,9 +1719,8 @@ C<nbd_pread>.";
"aio_pread_callback", {
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")] } );
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")] };
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1755,12 +1748,11 @@ cause a deadlock.";
"aio_pread_structured", {
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
- Closure (true,
- { cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset";
- Int "status";
- Mutable (Int "error");]} );
+ Closure { cbname="chunk";
+ cbargs=[BytesIn ("subbuf", "count");
+ UInt64 "offset";
+ Int "status";
+ Mutable (Int "error");]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1777,16 +1769,14 @@ documented in C<nbd_pread_structured>.";
"aio_pread_structured_callback", {
default_call with
args = [ BytesPersistOut ("buf", "count"); UInt64
"offset";
- Closure (true,
- { cbname="chunk";
- cbargs=[BytesIn ("subbuf",
"count");
- UInt64 "offset";
- Int "status";
- Mutable (Int "error"); ]});
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie";
- Mutable (Int "error"); ]} );
+ Closure { cbname="chunk";
+ cbargs=[BytesIn ("subbuf", "count");
+ UInt64 "offset";
+ Int "status";
+ Mutable (Int "error"); ]};
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie";
+ Mutable (Int "error"); ]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1829,9 +1819,8 @@ C<nbd_pwrite>.";
"aio_pwrite_callback", {
default_call with
args = [ BytesPersistIn ("buf", "count"); UInt64
"offset";
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1894,9 +1883,8 @@ Parameters behave as documented in
C<nbd_flush>.";
"aio_flush_callback", {
default_call with
- args = [ Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ args = [ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1937,9 +1925,8 @@ Parameters behave as documented in
C<nbd_trim>.";
"aio_trim_callback", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -1980,9 +1967,8 @@ Parameters behave as documented in
C<nbd_cache>.";
"aio_cache_callback", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2023,9 +2009,8 @@ Parameters behave as documented in
C<nbd_zero>.";
"aio_zero_callback", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2052,12 +2037,11 @@ cause a deadlock.";
"aio_block_status", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (true,
- { cbname="extent";
- cbargs=[String "metacontext"; UInt64
"offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")] } );
+ Closure { cbname="extent";
+ cbargs=[String "metacontext"; UInt64
"offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")] };
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -2073,15 +2057,13 @@ Parameters behave as documented in
C<nbd_block_status>.";
"aio_block_status_callback", {
default_call with
args = [ UInt64 "count"; UInt64 "offset";
- Closure (true,
- { cbname="extent";
- cbargs=[String "metacontext"; UInt64
"offset";
- ArrayAndLen (UInt32 "entries",
- "nr_entries");
- Mutable (Int "error")]});
- Closure (true,
- { cbname="callback";
- cbargs=[Int64 "cookie"; Mutable (Int
"error")]} );
+ Closure { cbname="extent";
+ cbargs=[String "metacontext"; UInt64
"offset";
+ ArrayAndLen (UInt32 "entries",
+ "nr_entries");
+ Mutable (Int "error")]};
+ Closure { cbname="callback";
+ cbargs=[Int64 "cookie"; Mutable (Int
"error")]};
Flags "flags" ];
ret = RInt64;
permitted_states = [ Connected ];
@@ -3121,7 +3103,8 @@ module C : sig
val generate_lib_unlocked_h : unit -> unit
val generate_lib_api_c : unit -> unit
val generate_docs_libnbd_api_pod : unit -> unit
- val print_arg_list : ?handle:bool -> ?user_data:bool -> ?types:bool
-> arg list -> unit
+ val print_arg_list : ?handle:bool -> ?valid_flag:bool ->
?user_data:bool ->
+ ?types:bool -> arg list -> unit
end = struct
(* Check the API definition. *)
@@ -3174,7 +3157,7 @@ let rec name_of_arg = function
| BytesOut (n, len) -> [n; len]
| BytesPersistIn (n, len) -> [n; len]
| BytesPersistOut (n, len) -> [n; len]
-| Closure (_, { cbname }) -> [cbname; sprintf "%s_user_data"
cbname ]
+| Closure { cbname } -> [cbname; sprintf "%s_user_data" cbname ]
| Flags n -> [n]
| Int n -> [n]
| Int64 n -> [n]
@@ -3187,7 +3170,8 @@ let rec name_of_arg = function
| UInt32 n -> [n]
| UInt64 n -> [n]
-let rec print_arg_list ?(handle = false) ?(user_data = false)
+let rec print_arg_list ?(handle = false) ?(valid_flag = false)
+ ?(user_data = false)
?(types = true) args pr "(";
let comma = ref false in
@@ -3196,6 +3180,12 @@ let rec print_arg_list ?(handle = false) ?(user_data =
false)
if types then pr "struct nbd_handle *";
pr "h"
);
+ if valid_flag then (
+ if !comma then pr ", ";
+ comma := true;
+ if types then pr "int ";
+ pr "valid_flag";
+ );
if user_data then (
if !comma then pr ", ";
comma := true;
@@ -3228,10 +3218,10 @@ let rec print_arg_list ?(handle = false) ?(user_data =
false)
pr "%s, " n;
if types then pr "size_t ";
pr "%s" len
- | Closure (_, { cbname; cbargs }) ->
+ | Closure { cbname; cbargs } ->
if types then (
pr "int (*%s) " cbname;
- print_arg_list ~user_data:true cbargs;
+ print_arg_list ~valid_flag:true ~user_data:true cbargs;
)
else
pr "%s" cbname;
@@ -3334,6 +3324,9 @@ let generate_include_libnbd_h () pr "\n";
List.iter (fun (n, i) -> pr "#define LIBNBD_%-30s %d\n" n i)
constants;
pr "\n";
+ pr "#define LIBNBD_CALLBACK_VALID 1\n";
+ pr "#define LIBNBD_CALLBACK_FREE 2\n";
+ pr "\n";
pr "extern struct nbd_handle *nbd_create (void);\n";
pr "#define LIBNBD_HAVE_NBD_CREATE 1\n";
pr "\n";
@@ -3795,27 +3788,14 @@ let print_python_binding name { args; ret } *)
List.iter (
function
- | Closure (persistent, { cbname; cbargs }) ->
- (* Persistent closures need an explicit function to decrement
- * the closure refcounts and free the user_data struct.
- *)
- if persistent then (
- pr "static void\n";
- pr "free_%s_%s_user_data (void *vp)\n" name cbname;
- pr "{\n";
- pr " PyObject *user_data = vp;\n";
- pr "\n";
- pr " Py_DECREF (user_data);\n";
- pr "}\n";
- pr "\n";
- );
-
+ | Closure { cbname; cbargs } ->
pr "/* Wrapper for %s callback of %s. */\n" cbname name;
pr "static int\n";
pr "%s_%s_wrapper " name cbname;
- C.print_arg_list ~user_data:true cbargs;
+ C.print_arg_list ~valid_flag:true ~user_data:true cbargs;
pr "\n";
pr "{\n";
+ pr " if (valid_flag & LIBNBD_CALLBACK_VALID) {\n";
pr " int ret;\n";
pr " PyGILState_STATE py_save = PyGILState_UNLOCKED;\n";
pr " PyObject *py_args, *py_ret;\n";
@@ -3927,6 +3907,12 @@ let print_python_binding name { args; ret } |
UInt _ | UInt32 _ -> assert false
) cbargs;
pr " return ret;\n";
+ pr " }\n";
+ pr "\n";
+ pr " if (valid_flag & LIBNBD_CALLBACK_FREE)\n";
+ pr " Py_DECREF ((PyObject *)user_data);\n";
+ pr "\n";
+ pr " return 0;\n";
pr "}\n";
pr "\n"
| _ -> ()
@@ -3966,7 +3952,7 @@ let print_python_binding name { args; ret } pr
" PyObject *%s; /* PyCapsule pointing to struct py_aio_buffer */\n"
n;
pr " struct py_aio_buffer *%s_buf;\n" n
- | Closure (_, { cbname }) ->
+ | Closure { cbname } ->
pr " PyObject *%s_user_data;\n" cbname
| Flags n ->
pr " uint32_t %s_u32;\n" n;
@@ -4032,7 +4018,7 @@ let print_python_binding name { args; ret } | BytesIn
(n, _) | BytesPersistIn (n, _)
| BytesPersistOut (n, _) -> pr ", &%s" n
| BytesOut (_, count) -> pr ", &%s" count
- | Closure (_, { cbname }) -> pr ", &%s_user_data" cbname
+ | Closure { cbname } -> pr ", &%s_user_data" cbname
| Flags n -> pr ", &%s" n
| Int n -> pr ", &%s" n
| Int64 n -> pr ", &%s" n
@@ -4048,13 +4034,12 @@ let print_python_binding name { args; ret } pr
"))\n";
pr " return NULL;\n";
- (* If the parameter has persistent closures then we need to
+ (* If the parameter has closures then we need to
* make sure the ref count remains positive.
*)
List.iter (
function
- | Closure (false, _) -> ()
- | Closure (true, { cbname }) ->
+ | Closure { cbname } ->
pr " Py_INCREF (%s_user_data);\n" cbname
| _ -> ()
) args;
@@ -4086,7 +4071,7 @@ let print_python_binding name { args; ret } pr
" %s = malloc (%s);\n" n count
| BytesPersistIn (n, _) | BytesPersistOut (n, _) ->
pr " %s_buf = nbd_internal_py_get_aio_buffer (%s);\n" n n
- | Closure (_, { cbname }) ->
+ | Closure { cbname } ->
pr " if (!PyCallable_Check (%s_user_data)) {\n" cbname;
pr " PyErr_SetString (PyExc_TypeError,\n";
pr " \"callback parameter %s is not
callable\");\n" cbname;
@@ -4122,7 +4107,7 @@ let print_python_binding name { args; ret } |
BytesOut (n, count) -> pr ", %s, %s" n count
| BytesPersistIn (n, _)
| BytesPersistOut (n, _) -> pr ", %s_buf->data,
%s_buf->len" n n
- | Closure (_, { cbname }) ->
+ | Closure { cbname } ->
pr ", %s_%s_wrapper" name cbname;
pr ", %s_user_data" cbname
| Flags n -> pr ", %s_u32" n
@@ -4200,11 +4185,7 @@ let print_python_binding name { args; ret } | Bool _
-> ()
| BytesIn (n, _) -> pr " PyBuffer_Release (&%s);\n" n
| BytesPersistIn _ | BytesOut _ | BytesPersistOut _ -> ()
- | Closure (false, _) -> ()
- | Closure (true, { cbname }) ->
- pr " /* This ensures the callback data is freed eventually.
*/\n";
- pr " nbd_add_close_callback (h, free_%s_%s_user_data,
%s_user_data);\n"
- name cbname cbname
+ | Closure _ -> ()
| Flags _ -> ()
| Int _ -> ()
| Int64 _ -> ()
@@ -4351,7 +4332,7 @@ class NBD (object):
| BytesIn (n, _) | BytesPersistIn (n, _) -> [n, None]
| BytesPersistOut (n, _) -> [n, None]
| BytesOut (_, count) -> [count, None]
- | Closure (_, { cbname }) -> [cbname, None]
+ | Closure { cbname } -> [cbname, None]
| Flags n -> [n, Some "0"]
| Int n -> [n, None]
| Int64 n -> [n, None]
@@ -4424,10 +4405,7 @@ let args_to_ocaml_args args | Flags n :: rest ->
Some (OCamlFlags n), List.rev rest
| _ -> None, args in
let args - List.map (
- function
- | a -> [OCamlArg a]
- ) args in
+ List.map (fun a -> [OCamlArg a]) args in
let args = List.flatten args in
match flags with
| Some f -> f :: OCamlHandle :: args
@@ -4450,7 +4428,7 @@ and ocaml_arg_to_string = function
| OCamlArg (BytesPersistIn _) -> "Buffer.t"
| OCamlArg (BytesOut _) -> "bytes"
| OCamlArg (BytesPersistOut _) -> "Buffer.t"
- | OCamlArg (Closure (_, { cbargs })) ->
+ | OCamlArg (Closure { cbargs }) ->
sprintf "(%s)"
(ocaml_fundecl_to_string (List.map (fun a -> OCamlArg a)
cbargs)
RErr)
@@ -4486,7 +4464,7 @@ let rec name_of_ocaml_arg = function
| BytesOut (n, len) -> n
| BytesPersistIn (n, len) -> n
| BytesPersistOut (n, len) -> n
- | Closure (_, { cbname }) -> cbname
+ | Closure { cbname } -> cbname
| Flags n -> n
| Int n -> n
| Int64 n -> n
@@ -4644,22 +4622,7 @@ let print_ocaml_binding (name, { args; ret }) (*
Functions with a callback parameter require special handling. *)
List.iter (
function
- | Closure (persistent, { cbname; cbargs }) ->
- (* Persistent closures need an explicit function to remove
- * the global root and free the user_data struct.
- *)
- if persistent then (
- pr "static void\n";
- pr "free_%s_%s_user_data (void *vp)\n" name cbname;
- pr "{\n";
- pr " value *user_data = vp;\n";
- pr "\n";
- pr " caml_remove_generational_global_root (user_data);\n";
- pr " free (user_data);\n";
- pr "}\n";
- pr "\n"
- );
-
+ | Closure { cbname; cbargs } ->
let argnames List.map (
function
@@ -4762,16 +4725,24 @@ let print_ocaml_binding (name, { args; ret }) pr
"\n";
pr "static int\n";
pr "%s_%s_wrapper " name cbname;
- C.print_arg_list ~user_data:true cbargs;
+ C.print_arg_list ~valid_flag:true ~user_data:true cbargs;
pr "\n";
pr "{\n";
- pr " int ret;\n";
+ pr " int ret = 0;\n";
pr "\n";
- pr " caml_leave_blocking_section ();\n";
- pr " ret = %s_%s_wrapper_locked " name cbname;
+ pr " if (valid_flag & LIBNBD_CALLBACK_VALID) {\n";
+ pr " caml_leave_blocking_section ();\n";
+ pr " ret = %s_%s_wrapper_locked " name cbname;
C.print_arg_list ~user_data:true ~types:false cbargs;
pr ";\n";
- pr " caml_enter_blocking_section ();\n";
+ pr " caml_enter_blocking_section ();\n";
+ pr " }\n";
+ pr "\n";
+ pr " if (valid_flag & LIBNBD_CALLBACK_FREE) {\n";
+ pr " caml_remove_generational_global_root ((value
*)user_data);\n";
+ pr " free (user_data);\n";
+ pr " }\n";
+ pr "\n";
pr " return ret;\n";
pr "}\n";
pr "\n"
@@ -4846,15 +4817,7 @@ let print_ocaml_binding (name, { args; ret }) pr
" struct nbd_buffer %s_buf = NBD_buffer_val (%sv);\n" n n;
pr " void *%s = %s_buf.data;\n" n n;
pr " size_t %s = %s_buf.len;\n" count n
- | OCamlArg (Closure (false, { cbname })) ->
- pr " /* This is safe because we only call this while this
stack\n";
- pr " * frame is live.\n";
- pr " */\n";
- pr " CAMLlocal1 (_%s_user_data);\n" cbname;
- pr " value *%s_user_data = &_%s_user_data;\n" cbname
cbname;
- pr " _%s_user_data = %sv;\n" cbname cbname;
- pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname
- | OCamlArg (Closure (true, { cbname })) ->
+ | OCamlArg (Closure { cbname }) ->
pr " /* The function may save a reference to the closure, so
we\n";
pr " * must treat it as a possible GC root.\n";
pr " */\n";
@@ -4863,9 +4826,7 @@ let print_ocaml_binding (name, { args; ret }) pr
" if (%s_user_data == NULL) caml_raise_out_of_memory ();\n" cbname;
pr " caml_register_generational_global_root
(%s_user_data);\n" cbname;
pr " *%s_user_data = %sv;\n" cbname cbname;
- pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname;
- pr " nbd_add_close_callback (h, free_%s_%s_user_data,
%s_user_data);\n"
- name cbname cbname
+ pr " const void *%s = %s_%s_wrapper;\n" cbname name cbname
| OCamlArg (Flags _) -> assert false (* see above *)
| OCamlArg (Int n) ->
pr " int %s = Int_val (%sv);\n" n n
diff --git a/generator/states-reply-simple.c b/generator/states-reply-simple.c
index 94875aa..d6b2e2c 100644
--- a/generator/states-reply-simple.c
+++ b/generator/states-reply-simple.c
@@ -64,7 +64,8 @@
int error = 0;
assert (cmd->error == 0);
- if (cmd->cb.fn.read (cmd->cb.fn_user_data, cmd->data,
cmd->count,
+ if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data,
+ cmd->data, cmd->count,
cmd->offset, LIBNBD_READ_DATA, &error) == -1)
cmd->error = error ? error : EPROTO;
}
diff --git a/generator/states-reply-structured.c
b/generator/states-reply-structured.c
index f60232e..2ef8d20 100644
--- a/generator/states-reply-structured.c
+++ b/generator/states-reply-structured.c
@@ -298,7 +298,7 @@
* current error rather than any earlier one. If the callback fails
* without setting errno, then use the server's error below.
*/
- if (cmd->cb.fn.read (cmd->cb.fn_user_data,
+ if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data,
cmd->data + (offset - cmd->offset),
0, offset, LIBNBD_READ_ERROR, &scratch) == -1)
if (cmd->error == 0)
@@ -385,7 +385,7 @@
if (cmd->cb.fn.read) {
int error = cmd->error;
- if (cmd->cb.fn.read (cmd->cb.fn_user_data,
+ if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data,
cmd->data + (offset - cmd->offset),
length - sizeof offset, offset,
LIBNBD_READ_DATA, &error) == -1)
@@ -447,7 +447,7 @@
if (cmd->cb.fn.read) {
int error = cmd->error;
- if (cmd->cb.fn.read (cmd->cb.fn_user_data,
+ if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data,
cmd->data + offset, length,
cmd->offset + offset,
LIBNBD_READ_HOLE, &error) == -1)
@@ -499,7 +499,7 @@
/* Call the caller's extent function. */
int error = cmd->error;
- if (cmd->cb.fn.extent (cmd->cb.fn_user_data,
+ if (cmd->cb.fn.extent (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data,
meta_context->name, cmd->offset,
&h->bs_entries[1], (length-4) / 4,
&error) == -1)
if (cmd->error == 0)
diff --git a/generator/states-reply.c b/generator/states-reply.c
index 1a0c149..b11479c 100644
--- a/generator/states-reply.c
+++ b/generator/states-reply.c
@@ -184,7 +184,8 @@ save_reply_state (struct nbd_handle *h)
if (cmd->cb.callback) {
int error = cmd->error;
- if (cmd->cb.callback (cmd->cb.user_data, cookie, &error) == -1
&& error)
+ if (cmd->cb.callback (LIBNBD_CALLBACK_VALID,
+ cmd->cb.user_data, cookie, &error) == -1
&& error)
cmd->error = error;
}
diff --git a/generator/states.c b/generator/states.c
index 69aa431..374b8c5 100644
--- a/generator/states.c
+++ b/generator/states.c
@@ -124,7 +124,8 @@ void abort_commands (struct nbd_handle *h,
int error = cmd->error ? cmd->error : ENOTCONN;
assert (cmd->type != NBD_CMD_DISC);
- if (cmd->cb.callback (cmd->cb.user_data, cmd->cookie,
+ if (cmd->cb.callback (LIBNBD_CALLBACK_VALID,
+ cmd->cb.user_data, cmd->cookie,
&error) == -1 && error)
cmd->error = error;
}
diff --git a/interop/dirty-bitmap.c b/interop/dirty-bitmap.c
index 8f0087d..5973696 100644
--- a/interop/dirty-bitmap.c
+++ b/interop/dirty-bitmap.c
@@ -42,11 +42,14 @@ struct data {
};
static int
-cb (void *opaque, const char *metacontext, uint64_t offset,
+cb (int valid_flag, void *opaque, const char *metacontext, uint64_t offset,
uint32_t *entries, size_t len, int *error)
{
struct data *data = opaque;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
/* libnbd does not actually verify that a server is fully compliant
* to the spec; the asserts marked [qemu-nbd] are thus dependent on
* the fact that qemu-nbd is compliant.
diff --git a/interop/structured-read.c b/interop/structured-read.c
index d00524f..ab659da 100644
--- a/interop/structured-read.c
+++ b/interop/structured-read.c
@@ -48,12 +48,16 @@ struct data {
};
static int
-read_cb (void *opaque, const void *bufv, size_t count, uint64_t offset,
+read_cb (int valid_flag, void *opaque,
+ const void *bufv, size_t count, uint64_t offset,
int status, int *error)
{
struct data *data = opaque;
const char *buf = bufv;
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
/* The NBD spec allows chunks to be reordered; we are relying on the
* fact that qemu-nbd does not do so.
*/
diff --git a/lib/aio.c b/lib/aio.c
index 8d7cb8d..de29b14 100644
--- a/lib/aio.c
+++ b/lib/aio.c
@@ -90,6 +90,17 @@ nbd_unlocked_aio_command_completed (struct nbd_handle *h,
else
h->cmds_done = cmd->next;
+ /* Free the callbacks. */
+ if (cmd->type != NBD_CMD_READ && cmd->cb.fn.extent)
+ cmd->cb.fn.extent (LIBNBD_CALLBACK_FREE, cmd->cb.fn_user_data,
+ NULL, 0, NULL, 0, NULL);
+ if (cmd->type == NBD_CMD_READ && cmd->cb.fn.read)
+ cmd->cb.fn.read (LIBNBD_CALLBACK_FREE, cmd->cb.fn_user_data,
+ NULL, 0, 0, 0, NULL);
+ if (cmd->cb.callback)
+ cmd->cb.callback (LIBNBD_CALLBACK_FREE, cmd->cb.user_data,
+ 0, NULL);
+
free (cmd);
/* If the command was successful, return true. */
diff --git a/lib/debug.c b/lib/debug.c
index 12c10f7..56a9455 100644
--- a/lib/debug.c
+++ b/lib/debug.c
@@ -40,9 +40,12 @@ nbd_unlocked_get_debug (struct nbd_handle *h)
int
nbd_unlocked_set_debug_callback (struct nbd_handle *h,
- int (*debug_fn) (void *, const char *, const
char *),
+ int (*debug_fn) (int, void *, const char *,
const char *),
void *data)
{
+ if (h->debug_fn)
+ /* ignore return value */
+ h->debug_fn (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL);
h->debug_fn = debug_fn;
h->debug_data = data;
return 0;
@@ -76,7 +79,7 @@ nbd_internal_debug (struct nbd_handle *h, const char *fs, ...)
if (h->debug_fn)
/* ignore return value */
- h->debug_fn (h->debug_data, context, msg);
+ h->debug_fn (LIBNBD_CALLBACK_VALID, h->debug_data, context, msg);
else
fprintf (stderr, "libnbd: debug: %s: %s\n", context ? :
"unknown", msg);
out:
diff --git a/lib/internal.h b/lib/internal.h
index b2a65bc..1790d01 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -80,7 +80,7 @@ struct nbd_handle {
/* For debugging. */
bool debug;
- int (*debug_fn) (void *, const char *, const char *);
+ int (*debug_fn) (int, void *, const char *, const char *);
void *debug_data;
/* Linked list of close callbacks. */
@@ -257,12 +257,14 @@ struct socket {
const struct socket_ops *ops;
};
-typedef int (*extent_fn) (void *user_data,
+typedef int (*extent_fn) (int valid_flag, void *user_data,
const char *metacontext, uint64_t offset,
uint32_t *entries, size_t nr_entries, int *error);
-typedef int (*read_fn) (void *user_data, const void *buf, size_t count,
+typedef int (*read_fn) (int valid_flag, void *user_data,
+ const void *buf, size_t count,
uint64_t offset, int status, int *error);
-typedef int (*callback_fn) (void *user_data, int64_t cookie, int *error);
+typedef int (*callback_fn) (int valid_flag, void *user_data,
+ int64_t cookie, int *error);
struct command_cb {
union {
diff --git a/tests/meta-base-allocation.c b/tests/meta-base-allocation.c
index 95e029b..b6a0e63 100644
--- a/tests/meta-base-allocation.c
+++ b/tests/meta-base-allocation.c
@@ -30,7 +30,7 @@
#include <libnbd.h>
-static int check_extent (void *data, const char *metacontext,
+static int check_extent (int valid_flag, void *data, const char *metacontext,
uint64_t offset,
uint32_t *entries, size_t nr_entries, int *error);
@@ -128,12 +128,17 @@ main (int argc, char *argv[])
}
static int
-check_extent (void *data, const char *metacontext,
+check_extent (int valid_flag, void *data, const char *metacontext,
uint64_t offset,
uint32_t *entries, size_t nr_entries, int *error)
{
size_t i;
- int id = * (int *)data;
+ int id;
+
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
+ id = * (int *)data;
printf ("extent: id=%d, metacontext=%s, offset=%" PRIu64 ",
"
"nr_entries=%zu, error=%d\n",
diff --git a/tests/oldstyle.c b/tests/oldstyle.c
index f4397d3..210fd52 100644
--- a/tests/oldstyle.c
+++ b/tests/oldstyle.c
@@ -37,10 +37,16 @@ static char wbuf[512] = { 1, 2, 3, 4 }, rbuf[512];
static const char *progname;
static int
-pread_cb (void *data, const void *buf, size_t count, uint64_t offset,
+pread_cb (int valid_flag, void *data,
+ const void *buf, size_t count, uint64_t offset,
int status, int *error)
{
- int *calls = data;
+ int *calls;
+
+ if (!(valid_flag & LIBNBD_CALLBACK_VALID))
+ return 0;
+
+ calls = data;
++*calls;
if (buf != rbuf || count != sizeof rbuf) {
--
2.22.0
Richard W.M. Jones
2019-Jul-24 12:17 UTC
[Libguestfs] [PATCH libnbd 3/3] lib: Remove nbd_add_close_callback.
We previously needed nbd_add_close_callback to do cleanup from
language bindings. However now we have closure lifetimes this is no
longer needed and can be removed.
See also:
https://www.redhat.com/archives/libguestfs/2019-July/msg00213.html
---
generator/generator | 18 ------------------
lib/handle.c | 35 -----------------------------------
lib/internal.h | 10 ----------
3 files changed, 63 deletions(-)
diff --git a/generator/generator b/generator/generator
index 5d5c267..9a15916 100755
--- a/generator/generator
+++ b/generator/generator
@@ -3139,7 +3139,6 @@ let generate_lib_libnbd_syms ()
pr "{\n";
pr " global:\n";
- pr " nbd_add_close_callback;\n";
pr " nbd_create;\n";
pr " nbd_close;\n";
pr " nbd_get_errno;\n";
@@ -3339,11 +3338,6 @@ let generate_include_libnbd_h () pr "extern int
nbd_get_errno (void);\n";
pr "#define LIBNBD_HAVE_NBD_GET_ERRNO 1\n";
pr "\n";
- pr "extern int nbd_add_close_callback (struct nbd_handle *h,\n";
- pr " nbd_close_callback cb,\n";
- pr " void *user_data);\n";
- pr "#define LIBNBD_HAVE_NBD_ADD_CLOSE_CALLBACK 1\n";
- pr "\n";
List.iter (
fun (name, { args; ret }) -> print_extern_and_define name args ret
) handle_calls;
@@ -3617,18 +3611,6 @@ errors have corresponding errnos, so even if there has
been an error
this may return C<0>. Error codes are the standard ones from
C<E<lt>errno.hE<gt>>.
-=head1 CLOSE CALLBACKS
-
-You can register close callbacks with the handle. These are
-called when C<nbd_close> is called. The order in which they
-are called is not defined. This API is only available
-from C and is designed to help when writing bindings to libnbd
-from other programming languages.
-
- typedef void (*nbd_close_callback) (void *user_data);
- int nbd_add_close_callback (struct nbd_handle *nbd,
- nbd_close_callback cb, void *user_data);
-
";
pr "=head1 API CALLS\n";
diff --git a/lib/handle.c b/lib/handle.c
index 9c643d8..78e72c5 100644
--- a/lib/handle.c
+++ b/lib/handle.c
@@ -90,18 +90,11 @@ nbd_create (void)
void
nbd_close (struct nbd_handle *h)
{
- struct close_callback *cc, *cc_next;
struct meta_context *m, *m_next;
if (h == NULL)
return;
- for (cc = h->close_callbacks; cc != NULL; cc = cc_next) {
- cc_next = cc->next;
- cc->cb (cc->user_data);
- free (cc);
- }
-
free (h->bs_entries);
for (m = h->meta_contexts; m != NULL; m = m_next) {
m_next = m->next;
@@ -198,34 +191,6 @@ nbd_unlocked_add_meta_context (struct nbd_handle *h, const
char *name)
return 0;
}
-/* This is not generated because we don't want to offer it to other
- * programming languages.
- */
-int
-nbd_add_close_callback (struct nbd_handle *h,
- nbd_close_callback cb, void *user_data)
-{
- int ret;
- struct close_callback *cc;
-
- pthread_mutex_lock (&h->lock);
- cc = malloc (sizeof *cc);
- if (cc == NULL) {
- set_error (errno, "malloc");
- ret = -1;
- goto out;
- }
- cc->next = h->close_callbacks;
- cc->cb = cb;
- cc->user_data = user_data;
- h->close_callbacks = cc;
-
- ret = 0;
- out:
- pthread_mutex_unlock (&h->lock);
- return ret;
-}
-
const char *
nbd_unlocked_get_package_name (struct nbd_handle *h)
{
diff --git a/lib/internal.h b/lib/internal.h
index 1790d01..d534243 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -45,7 +45,6 @@
#define MAX_REQUEST_SIZE (64 * 1024 * 1024)
struct meta_context;
-struct close_callback;
struct socket;
struct command;
@@ -83,9 +82,6 @@ struct nbd_handle {
int (*debug_fn) (int, void *, const char *, const char *);
void *debug_data;
- /* Linked list of close callbacks. */
- struct close_callback *close_callbacks;
-
/* State machine.
*
* The actual current state is ‘state’. ‘public_state’ is updated
@@ -225,12 +221,6 @@ struct meta_context {
uint32_t context_id; /* Context ID negotiated with the server. */
};
-struct close_callback {
- struct close_callback *next; /* Linked list. */
- nbd_close_callback cb; /* Function. */
- void *user_data; /* Data. */
-};
-
struct socket_ops {
ssize_t (*recv) (struct nbd_handle *h,
struct socket *sock, void *buf, size_t len);
--
2.22.0
Eric Blake
2019-Jul-24 15:02 UTC
Re: [Libguestfs] [PATCH libnbd 1/3] generator: Change Closure so it describes single callbacks.
On 7/24/19 7:17 AM, Richard W.M. Jones wrote:> In preparation for closure lifetimes, split up the Closure so it no > longer describes a list of closures, but a single callback. > > This changes the API because functions which take 2 or more closures > now pass a separate user_data for each one. > --- > docs/libnbd.pod | 3 +- > examples/strict-structured-reads.c | 2 +- > generator/generator | 760 ++++++++++++---------------- > generator/states-reply-simple.c | 2 +- > generator/states-reply-structured.c | 8 +- > lib/internal.h | 3 +- > lib/rw.c | 32 +- > 7 files changed, 364 insertions(+), 446 deletions(-) > > diff --git a/docs/libnbd.pod b/docs/libnbd.pod > index 5608e63..631bb3b 100644 > --- a/docs/libnbd.pod > +++ b/docs/libnbd.pod > @@ -487,8 +487,7 @@ C<nbd_set_debug_callback>, C<nbd_pread_callback>). Libnbd can call > these functions while processing. > > Callbacks have an opaque C<void *user_data> pointer. This is passedShould we tweak this to explicitly call out "Callbacks in the C language", to differentiate it from bindings to other languages that do not do this?> -as the first parameter to the callback. libnbd functions that take > -two callback pointers share the same opaque data for both calls. > +as the first parameter to the callback. >> +++ b/generator/generator > @@ -849,10 +849,10 @@ and arg > written by the function *) > | BytesPersistIn of string * string (* same as above, but buffer persists *) > | BytesPersistOut of string * string > -| Closure of bool * closure list (* void *opaque + one or more closures > - flag if true means callbacks persist > - in the handle, false means they only > - exist during the function call *) > +| Closure of bool * closure (* function pointer + void *opaque > + flag if true means callbacks persist > + in the handle, false means they only > + exist during the function call *)Do we still need the closure record type, or can/should we simplify further to: | Closure of bool * string * arg list (and later in the series, even further by dropping 'bool *')> | Flags of string (* NBD_CMD_FLAG_* flags *) > | Int of string (* small int *) > | Int64 of string (* 64 bit signed int *) > @@ -921,8 +921,8 @@ Return the state of the debug flag on this handle."; > "set_debug_callback", { > default_call with > args = [ Closure (true, > - [{ cbname="debug_fn"; > - cbargs=[String "context"; String "msg"] }]) ]; > + { cbname="debug_fn"; > + cbargs=[String "context"; String "msg"] }) ];Keeping the record type means that you still have to provide names, vs. directly using tuples where we'd write: args = [ Closure (true, "debug_fn", [String "context"; String "msg"]) ];> @@ -3811,154 +3795,140 @@ let print_python_binding name { args; ret } > *) > List.iter ( > function > - | Closure (persistent, cls) -> > - pr "struct %s_user_data {\n" name; > - List.iter ( > - fun { cbname } -> > - pr " PyObject *%s;\n" cbname > - ) cls; > - pr "};\n"; > - pr "\n"; > - > + | Closure (persistent, { cbname; cbargs }) -> > (* Persistent closures need an explicit function to decrement > * the closure refcounts and free the user_data struct.Comment needs a touchup now that there is no user_data struct.> *) > if persistent then ( > pr "static void\n"; > - pr "free_%s_user_data (void *vp)\n" name; > + pr "free_%s_%s_user_data (void *vp)\n" name cbname; > pr "{\n"; > - pr " struct %s_user_data *user_data = vp;\n" name; > + pr " PyObject *user_data = vp;\n"; > pr "\n"; > - List.iter ( > - fun { cbname } -> > - pr " Py_DECREF (user_data->%s);\n" cbname > - ) cls; > - pr " free (user_data);\n"; > + pr " Py_DECREF (user_data);\n"; > pr "}\n"; > pr "\n"; > );... (lots of churn due to reindentation, such is life)> + pr " py_args = Py_BuildValue (\"(\""; > + List.iter ( > + function > + | ArrayAndLen (UInt32 n, len) -> pr " \"O\"" > + | BytesIn (n, len) -> pr " \"y#\"" > + | Int n -> pr " \"i\"" > + | Int64 n -> pr " \"L\"" > + | Mutable (Int n) -> pr " \"O\"" > + | String n -> pr " \"s\"" > + | UInt64 n -> pr " \"K\"" > + (* The following not yet implemented for callbacks XXX *) > + | ArrayAndLen _ | Bool _ | BytesOut _ > + | BytesPersistIn _ | BytesPersistOut _Not your usual indentation style.> + | Closure _ > + | Flags _ | Mutable _ > + | Path _ | SockAddrAndLen _ | StringList _ > + | UInt _ | UInt32 _ -> assert false > + ) cbargs; > + pr " \")\""; > + List.iter ( > + function > + | ArrayAndLen (UInt32 n, _) -> pr ", py_%s" n > + | BytesIn (n, len) -> pr ", %s, (int) %s" n len > + | Mutable (Int n) -> pr ", py_%s" n > + | Int n | Int64 n > + | String n > + | UInt64 n -> pr ", %s" n > + (* The following not yet implemented for callbacks XXX *) > + | ArrayAndLen _ | Bool _ | BytesOut _ > + | BytesPersistIn _ | BytesPersistOut _ > + | Closure _ > + | Flags _ | Mutable _ > + | Path _ | SockAddrAndLen _ | StringList _ > + | UInt _ | UInt32 _ -> assert falseMore instances of what appears to be emacs indenting differently from your preferences.> @@ -4031,19 +3998,6 @@ let print_python_binding name { args; ret } > ) args; > pr "\n"; > > - (* Allocate the persistent closure user_data. *) > - List.iter ( > - function > - | Closure (false, _) -> () > - | Closure (true, cls) -> > - pr " user_data = malloc (sizeof *user_data);\n"; > - pr " if (user_data == NULL) {\n"; > - pr " PyErr_NoMemory ();\n"; > - pr " return NULL;\n"; > - pr " }\n" > - | _ -> () > - ) args;Nice that we get rid of this. Overall, the patch makes sense; I assume you can fix any problems I pointed out above without needing to send v2 (especially since this is mostly OCaml, where I defer to your experience anyway) -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
Eric Blake
2019-Jul-24 15:18 UTC
Re: [Libguestfs] [PATCH libnbd 2/3] lib: Implement closure lifetimes.
On 7/24/19 7:17 AM, Richard W.M. Jones wrote:> Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures was > wasteful as we needed to register a "close callback" to free the > closure when the handle is closed. But if you had submitted thousands > of asynchronous commands you would end up registering thousands of > close callbacks. > > We actually have far more information about the lifetime of closures. > We know precisely when they will no longer be needed by the library. > Callers can use this information to free up associated user data > earlier. In particular in language bindings we can remove roots / > decrement reference counts at the right place to free the closure, > without waiting for the handle to be closed. > > The solution to this is to introduce the concept of a closure > lifetime. The callback is called with an extra valid_flag parameter > which is a bitmap containing LIBNBD_CALLBACK_VALID and/or > LIBNBD_CALLBACK_FREE. LIBNBD_CALLBACK_VALID corresponds to a normal > call of the callback function by the library. After the library has > finished with the callback (declaring that this callback will never be > needed or called again), it is called once more with > valid_flag == LIBNBD_CALLBACK_FREE. > > (Note it is also possible for the library to call the callback with > valid_flag == LIBNBD_CALLBACK_VALID|LIBNBD_CALLBACK_FREE, meaning it's the > last valid call.) >> > diff --git a/docs/libnbd.pod b/docs/libnbd.pod > index 631bb3b..e9a6030 100644 > --- a/docs/libnbd.pod > +++ b/docs/libnbd.pod > @@ -487,7 +487,59 @@ C<nbd_set_debug_callback>, C<nbd_pread_callback>). Libnbd can call > these functions while processing. > > Callbacks have an opaque C<void *user_data> pointer. This is passed > -as the first parameter to the callback. > +as the second parameter to the callback. > + > +=head2 Callback lifetimes > + > +All callbacks have an C<int valid_flag> parameter which is used to > +help with the lifetime of the callback. C<valid_flag> contains the > +I<logical or> of:Again, worth mentioning that this explicitly only for the C bindings?> + > +=over 4 > + > +=item C<LIBNBD_CALLBACK_VALID> > + > +The callback parameters are valid and this is a normal callback. > + > +=item C<LIBNBD_CALLBACK_FREE> > + > +This is the last time the library will call this function. Any data > +associated with the callback can be freed. > + > +=item other bits > + > +Other bits in C<valid_flag> should be ignored.Are we guaranteeing never to set other bits, or that other bits will be 0 for now and only set later if the client opts in to whatever the new bits are useful for? But I'm okay with leaving this sentence as worded.> + > +=back > + > +For example C<nbd_set_debug_callback> sets up a callback which you > +could define like this: > + > + int my_debug_fn (int valid_flag, void *user_data, > + const char *context, const char *msg) > + { > + if (valid_flag & LIBNBD_CALLBACK_VALID) { > + printf ("context = %s, msg = %s\n", context, msg); > + } > + if (valid_flag & LIBNBD_CALLBACK_FREE) { > + /* If you need to free something, for example: */ > + free (user_data); > + } > + return 0; > + } > + > +If you don't care about the freeing feature then it is also correct to > +write this: > + > + int my_debug_fn (int valid_flag, void *user_data, > + const char *context, const char *msg) > + { > + if (!(valid_flag & LIBNBD_CALLBACK_VALID)) return 0; > + > + // Rest of callback as normal. > + }Both examples are good.> +++ b/examples/strict-structured-reads.c > @@ -51,12 +51,16 @@ static int64_t total_bytes; > static int total_success; > > static int > -read_chunk (void *opaque, const void *bufv, size_t count, uint64_t offset, > +read_chunk (int valid_flag, void *opaque, > + const void *bufv, size_t count, uint64_t offset, > int status, int *error) > { > struct data *data = opaque; > struct range *r, **prev; > > + if (!(valid_flag & LIBNBD_CALLBACK_VALID)) > + return 0; > +This one is okay (since we pass the same opaque to both this function and the later callback function, so have nothing to free at the last use of this one)...> /* libnbd guarantees this: */ > assert (offset >= data->offset); > assert (offset + count <= data->offset + data->count); > @@ -127,11 +131,14 @@ read_chunk (void *opaque, const void *bufv, size_t count, uint64_t offset, > } > > static int > -read_verify (void *opaque, int64_t cookie, int *error) > +read_verify (int valid_flag, void *opaque, int64_t cookie, int *error) > { > struct data *data = opaque; > int ret = -1; > > + if (!(valid_flag & LIBNBD_CALLBACK_VALID)) > + return 0;...but this one is wrong; it calls free(data) which should be deferred to the valid_flag & LIBNBD_CALLBACK_FREE portion. (It looks like later on in the patch, I see that the nbd_aio_FOO_callback callback is always called exactly once with VALID|FREE, so your bug here is masked because of that calling convention - but we should really fix this one to be a better example).> +++ b/generator/generator > @@ -849,10 +849,7 @@ and arg > written by the function *) > | BytesPersistIn of string * string (* same as above, but buffer persists *) > | BytesPersistOut of string * string > -| Closure of bool * closure (* function pointer + void *opaque > - flag if true means callbacks persist > - in the handle, false means they only > - exist during the function call *) > +| Closure of closure (* function pointer + void *opaque *)Re-echoing my comment in 1/3, writing this as 'Closure of string * arg list' may seem cleaner (certainly less typing below).> @@ -3196,6 +3180,12 @@ let rec print_arg_list ?(handle = false) ?(user_data = false) > if types then pr "struct nbd_handle *"; > pr "h" > ); > + if valid_flag then ( > + if !comma then pr ", "; > + comma := true; > + if types then pr "int "; > + pr "valid_flag";Should this be 'unsigned int valid_flag', as bitmasks over signed values have awkward semantics if you touch the sign bit? But I'm okay with int for now, as it matches 'int nbd_aio_get_direction(...)' and nbd_pread_structured using 'int status' in its callback.> @@ -3228,10 +3218,10 @@ let rec print_arg_list ?(handle = false) ?(user_data = false) > pr "%s, " n; > if types then pr "size_t "; > pr "%s" len > - | Closure (_, { cbname; cbargs }) -> > + | Closure { cbname; cbargs } -> > if types then ( > pr "int (*%s) " cbname; > - print_arg_list ~user_data:true cbargs; > + print_arg_list ~valid_flag:true ~user_data:true cbargs;Indentation.> + | Closure { cbname; cbargs } -> > pr "/* Wrapper for %s callback of %s. */\n" cbname name; > pr "static int\n"; > pr "%s_%s_wrapper " name cbname; > - C.print_arg_list ~user_data:true cbargs; > + C.print_arg_list ~valid_flag:true ~user_data:true cbargs; > pr "\n"; > pr "{\n"; > + pr " if (valid_flag & LIBNBD_CALLBACK_VALID) {\n"; > pr " int ret;\n"; > pr " PyGILState_STATE py_save = PyGILState_UNLOCKED;\n";Do we care about the generated indentation looking sane? (That can be a followup patch, to minimize the churn on this one...)> pr " PyObject *py_args, *py_ret;\n"; > @@ -3927,6 +3907,12 @@ let print_python_binding name { args; ret } > | UInt _ | UInt32 _ -> assert false > ) cbargs; > pr " return ret;\n"; > + pr " }\n";Ouch. Calling 'return ret' before checking for LIBNBD_CALLBACK_FREE is liable to leak. I think you have to defer the return...> + pr "\n"; > + pr " if (valid_flag & LIBNBD_CALLBACK_FREE)\n"; > + pr " Py_DECREF ((PyObject *)user_data);\n"; > + pr "\n"; > + pr " return 0;\n";...to here.> @@ -4048,13 +4034,12 @@ let print_python_binding name { args; ret } > pr "))\n"; > pr " return NULL;\n"; > > - (* If the parameter has persistent closures then we need to > + (* If the parameter has closures then we need to > * make sure the ref count remains positive. > *) > List.iter ( > function > - | Closure (false, _) -> () > - | Closure (true, { cbname }) -> > + | Closure { cbname } ->Now that this match...> pr " Py_INCREF (%s_user_data);\n" cbname > | _ -> () > ) args; > @@ -4086,7 +4071,7 @@ let print_python_binding name { args; ret } > pr " %s = malloc (%s);\n" n count > | BytesPersistIn (n, _) | BytesPersistOut (n, _) -> > pr " %s_buf = nbd_internal_py_get_aio_buffer (%s);\n" n n > - | Closure (_, { cbname }) -> > + | Closure { cbname } -> > pr " if (!PyCallable_Check (%s_user_data)) {\n" cbname; > pr " PyErr_SetString (PyExc_TypeError,\n"; > pr " \"callback parameter %s is not callable\");\n" cbname;...and this match are identical, should we group the code?> +++ b/generator/states-reply-simple.cI got this far in my review; I'll resume later... -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
Eric Blake
2019-Jul-24 17:21 UTC
Re: [Libguestfs] [PATCH libnbd 2/3] lib: Implement closure lifetimes.
On 7/24/19 7:17 AM, Richard W.M. Jones wrote:> Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures was > wasteful as we needed to register a "close callback" to free the > closure when the handle is closed. But if you had submitted thousands > of asynchronous commands you would end up registering thousands of > close callbacks.Our mails are crossing; I had typed this up (so I'm sending now) even though I already see that you've tweaked things in v2. I've got two threads of thoughts below.> > (Note it is also possible for the library to call the callback with > valid_flag == LIBNBD_CALLBACK_VALID|LIBNBD_CALLBACK_FREE, meaning it's the > last valid call.)[1] In my previous reply, I assumed that the nbd_aio_FOO_callback function would use this paradigm...> +++ b/examples/strict-structured-reads.c> @@ -127,11 +131,14 @@ read_chunk (void *opaque, const void *bufv, size_t count, uint64_t offset, > } > > static int > -read_verify (void *opaque, int64_t cookie, int *error) > +read_verify (int valid_flag, void *opaque, int64_t cookie, int *error) > { > struct data *data = opaque; > int ret = -1; > > + if (!(valid_flag & LIBNBD_CALLBACK_VALID)) > + return 0; > +[1] which in turn affected this code (calling free(data) on the first VALID call rather than on the FREE call is fishy), but now that I've actually read the rest of the patch...> +++ b/generator/states-reply-simple.c > @@ -64,7 +64,8 @@ > int error = 0; > > assert (cmd->error == 0); > - if (cmd->cb.fn.read (cmd->cb.fn_user_data, cmd->data, cmd->count, > + if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data, > + cmd->data, cmd->count, > cmd->offset, LIBNBD_READ_DATA, &error) == -1)[2] Here, we know we are calling the read callback exactly once, so we could pass DATA|FREE here.> cmd->error = error ? error : EPROTO; > } > diff --git a/generator/states-reply-structured.c b/generator/states-reply-structured.c > index f60232e..2ef8d20 100644 > --- a/generator/states-reply-structured.c > +++ b/generator/states-reply-structured.c > @@ -298,7 +298,7 @@ > * current error rather than any earlier one. If the callback fails > * without setting errno, then use the server's error below. > */ > - if (cmd->cb.fn.read (cmd->cb.fn_user_data, > + if (cmd->cb.fn.read (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data, > cmd->data + (offset - cmd->offset),[2] Here, we know if we will NOT call the read callback again if NBD_REPLY_FLAG_DONE is set (so if it is set, we could pass VALID|FREE here; but if it is not set, we still have to take care of passing FREE later).> @@ -499,7 +499,7 @@ > /* Call the caller's extent function. */ > int error = cmd->error; > > - if (cmd->cb.fn.extent (cmd->cb.fn_user_data, > + if (cmd->cb.fn.extent (LIBNBD_CALLBACK_VALID, cmd->cb.fn_user_data, > meta_context->name, cmd->offset, > &h->bs_entries[1], (length-4) / 4, &error) == -1)[2] Same - if NBD_REPLY_FLAG_DONE is set, we could pass VALID|FREE here, but if it is clear, we have to defer FREE to later. Note that state REPLY.STRUCTURED_REPLY.FINISH would be such a spot where we could call the FREE flag. On the other hand, if we let that state always call with FREE, it's easier to code that than it is to code it to call FREE only if the earlier code for chunk/extents did not call VALID|FREE. So for the structured reply spots marked [2] above, calling with just VALID and then having FINISH do FREE unconditionally is worth considering (the simple reply can still do VALID|FREE at once). But if we do that...> if (cmd->error == 0) > diff --git a/generator/states-reply.c b/generator/states-reply.c > index 1a0c149..b11479c 100644 > --- a/generator/states-reply.c > +++ b/generator/states-reply.c > @@ -184,7 +184,8 @@ save_reply_state (struct nbd_handle *h) > if (cmd->cb.callback) { > int error = cmd->error; > > - if (cmd->cb.callback (cmd->cb.user_data, cookie, &error) == -1 && error) > + if (cmd->cb.callback (LIBNBD_CALLBACK_VALID, > + cmd->cb.user_data, cookie, &error) == -1 && error)[1] ...we know that this is the only time we'll invoke this callback, so we could have passed VALID|FREE here. (And this part definitely means I have to respin my proposal to let the callback return 1 to auto-retire).> cmd->error = error; > } > > diff --git a/generator/states.c b/generator/states.c > index 69aa431..374b8c5 100644 > --- a/generator/states.c > +++ b/generator/states.c > @@ -124,7 +124,8 @@ void abort_commands (struct nbd_handle *h, > int error = cmd->error ? cmd->error : ENOTCONN; > > assert (cmd->type != NBD_CMD_DISC); > - if (cmd->cb.callback (cmd->cb.user_data, cmd->cookie, > + if (cmd->cb.callback (LIBNBD_CALLBACK_VALID, > + cmd->cb.user_data, cmd->cookie,[1] another spot where we only call things once, and so we could pass VALID|FREE.> +++ b/lib/aio.c > @@ -90,6 +90,17 @@ nbd_unlocked_aio_command_completed (struct nbd_handle *h, > else > h->cmds_done = cmd->next; > > + /* Free the callbacks. */ > + if (cmd->type != NBD_CMD_READ && cmd->cb.fn.extent) > + cmd->cb.fn.extent (LIBNBD_CALLBACK_FREE, cmd->cb.fn_user_data, > + NULL, 0, NULL, 0, NULL); > + if (cmd->type == NBD_CMD_READ && cmd->cb.fn.read) > + cmd->cb.fn.read (LIBNBD_CALLBACK_FREE, cmd->cb.fn_user_data, > + NULL, 0, 0, 0, NULL);[2] ...these FREE calls could instead live in REPLY.STRUCTURED_REPLY.FINISH> + if (cmd->cb.callback) > + cmd->cb.callback (LIBNBD_CALLBACK_FREE, cmd->cb.user_data, > + 0, NULL);[1] and this spot is useless for my auto-retire patch, hence my idea of using VALID|FREE at both spots where we utilize the callback, rather than here where we retire the callback. I'll have to look at your v2, and my ideas for rearranging the callbacks could still be done as a patch on top of your initial implementation, rather than making you have to spin a v3, since our mails have crossed.> + > free (cmd); > > /* If the command was successful, return true. */ > diff --git a/lib/debug.c b/lib/debug.c > index 12c10f7..56a9455 100644 > --- a/lib/debug.c > +++ b/lib/debug.c > @@ -40,9 +40,12 @@ nbd_unlocked_get_debug (struct nbd_handle *h) > > int > nbd_unlocked_set_debug_callback (struct nbd_handle *h, > - int (*debug_fn) (void *, const char *, const char *), > + int (*debug_fn) (int, void *, const char *, const char *), > void *data) > { > + if (h->debug_fn) > + /* ignore return value */ > + h->debug_fn (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL);This frees the first debug callback when installing a second; but where does nbd_close free the second? Also, do we allow C code to pass NULL to uninstall a handler? Should other languages be able to clear out a callback? -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
Apparently Analagous Threads
- [PATCH libnbd v2 2/5] lib: Implement closure lifetimes.
- [PATCH libnbd 1/2] generator: Handle closure args (cbargs) specially.
- [PATCH libnbd v2] generator: Define new Closure type instead of callbacks.
- [PATCH libnbd 2/3] lib: Implement closure lifetimes.
- [PATCH libnbd v3 1/2] lib: Implement closure lifetimes.