Libguestfs - Apr 2020 - Re: [PATCH nbdkit] server/locks: Allow lock_request to be called when there is no current conn.

On Haiku tests/test-socket-activation failed with:

nbdkit: locks.c:96:lock_request: conn != NULL

called from server/sockets.c: accept_connection
in the fallback path which does:
  lock_request ();
  thread_data->sock = set_cloexec (accept (listen_sock, NULL, NULL));
  unlock_request ()

Because there is no current connection in this thread this code fails.

However it should be possible to call lock_request without a
connection, provided that
thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS (which it is
when the fallback path is engaged on Haiku).  There was a regression
caused when I modified to code to use an implicit TLS connection.

Fixes commit 91023f269d4cea56f573a1aa0d880b12052f6e1e.
---
 server/locks.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/server/locks.c b/server/locks.c
index 5d54d311..9269c75e 100644
--- a/server/locks.c
+++ b/server/locks.c
@@ -93,7 +93,7 @@ unlock_connection (void)
 void
 lock_request (void)
 {
-  GET_CONN;
+  struct connection *conn = threadlocal_get_conn ();
 
   if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS &&
       pthread_mutex_lock (&all_requests_lock))
@@ -110,7 +110,7 @@ lock_request (void)
 void
 unlock_request ()
 {
-  GET_CONN;
+  struct connection *conn = threadlocal_get_conn ();
 
   if (pthread_rwlock_unlock (&unload_prevention_lock))
     abort ();
-- 
2.25.0

On 4/28/20 11:45 AM, Richard W.M. Jones wrote:
> On Haiku tests/test-socket-activation failed with:
> 
> nbdkit: locks.c:96:lock_request: conn != NULL
> 
> called from server/sockets.c: accept_connection
> in the fallback path which does:
>    lock_request ();
>    thread_data->sock = set_cloexec (accept (listen_sock, NULL, NULL));
>    unlock_request ()
> 
> Because there is no current connection in this thread this code fails.
> 
> However it should be possible to call lock_request without a
> connection, provided that
> thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS (which it is
> when the fallback path is engaged on Haiku).  There was a regression
> caused when I modified to code to use an implicit TLS connection.
> 
> Fixes commit 91023f269d4cea56f573a1aa0d880b12052f6e1e.
> ---
>   server/locks.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
ACK

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Tue, Apr 28, 2020 at 12:29:47PM -0500, Eric Blake
wrote:
> On 4/28/20 11:45 AM, Richard W.M. Jones wrote:
> >On Haiku tests/test-socket-activation failed with:
> >
> >nbdkit: locks.c:96:lock_request: conn != NULL
> >
> >called from server/sockets.c: accept_connection
> >in the fallback path which does:
> >   lock_request ();
> >   thread_data->sock = set_cloexec (accept (listen_sock, NULL,
NULL));
> >   unlock_request ()
> >
> >Because there is no current connection in this thread this code fails.
> >
> >However it should be possible to call lock_request without a
> >connection, provided that
> >thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS (which it is
> >when the fallback path is engaged on Haiku).  There was a regression
> >caused when I modified to code to use an implicit TLS connection.
> >
> >Fixes commit 91023f269d4cea56f573a1aa0d880b12052f6e1e.
> >---
> >  server/locks.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> ACK
Thanks - I tidied up the commit message a bit when I pushed it.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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live CD or over the network (PXE) and turn machines into KVM guests.
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