Ian Jackson
2013-Nov-12 15:34 UTC
[PATCH v2] libxl: Introduce nested async operations (nested ao)
Roger Pau Monne writes ("[PATCH v2 01/10] libxl: Introduce nested async operations (nested ao)"):> This allows a long-running ao to avoid accumulating memory. Each > nested ao has its own gc.Thanks. Ian C wanted an improved comment, so: From: Ian Jackson <ian.jackson@eu.citrix.com> Date: Mon, 4 Nov 2013 17:56:15 +0000 Subject: [PATCH] libxl: Introduce nested async operations (nested ao) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This allows a long-running ao to avoid accumulating memory. Each nested ao has its own gc. Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com> Cc: Roger Pau Monné <roger.pau@citrix.com> Cc: Ian Campbell <ian.campbell@citrix.com> --- v2: Mention in comment that multiple levels of nesting is OK. --- tools/libxl/libxl_event.c | 35 +++++++++++++++++++++++++++++++++++ tools/libxl/libxl_internal.h | 25 ++++++++++++++++++++++++- 2 files changed, 59 insertions(+), 1 deletion(-) diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c index 0fe4428..54d15db 100644 --- a/tools/libxl/libxl_event.c +++ b/tools/libxl/libxl_event.c @@ -1572,6 +1572,7 @@ void libxl__ao_complete(libxl__egc *egc, libxl__ao *ao, int rc) LOG(DEBUG,"ao %p: complete, rc=%d",ao,rc); assert(ao->magic == LIBXL__AO_MAGIC); assert(!ao->complete); + assert(!ao->nested); ao->complete = 1; ao->rc = rc; @@ -1736,6 +1737,7 @@ void libxl__ao_progress_report(libxl__egc *egc, libxl__ao *ao, const libxl_asyncprogress_how *how, libxl_event *ev) { AO_GC; + assert(!ao->nested); if (how->callback == dummy_asyncprogress_callback_ignore) { LOG(DEBUG,"ao %p: progress report: ignored",ao); libxl_event_free(CTX,ev); @@ -1756,6 +1758,39 @@ void libxl__ao_progress_report(libxl__egc *egc, libxl__ao *ao, } +/* nested ao */ + +_hidden libxl__ao *libxl__nested_ao_create(libxl__ao *parent) +{ + /* We only use the parent to get the ctx. However, we require the + * caller to provide us with an ao, not just a ctx, to prove that + * they are already in an asynchronous operation. That will avoid + * people using this to (for example) make an ao in a non-ao_how + * function somewhere in the middle of libxl. */ + libxl__ao *child = NULL; + libxl_ctx *ctx = libxl__gc_owner(&parent->gc); + + assert(parent->magic == LIBXL__AO_MAGIC); + + child = libxl__zalloc(&ctx->nogc_gc, sizeof(*child)); + child->magic = LIBXL__AO_MAGIC; + child->nested = 1; + LIBXL_INIT_GC(child->gc, ctx); + libxl__gc *gc = &child->gc; + + LOG(DEBUG,"ao %p: nested ao, parent %p", child, parent); + return child; +} + +_hidden void libxl__nested_ao_free(libxl__ao *child) +{ + assert(child->magic == LIBXL__AO_MAGIC); + assert(child->nested); + libxl_ctx *ctx = libxl__gc_owner(&child->gc); + libxl__ao__destroy(ctx, child); +} + + /* * Local variables: * mode: C diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h index 4729566..0b20434 100644 --- a/tools/libxl/libxl_internal.h +++ b/tools/libxl/libxl_internal.h @@ -427,7 +427,7 @@ struct libxl__ao { * only in libxl__ao_complete.) */ uint32_t magic; - unsigned constructing:1, in_initiator:1, complete:1, notified:1; + unsigned constructing:1, in_initiator:1, complete:1, notified:1, nested:1; int progress_reports_outstanding; int rc; libxl__gc gc; @@ -1780,6 +1780,29 @@ _hidden void libxl__ao_complete_check_progress_reports(libxl__egc*, libxl__ao*); /* + * Short-lived sub-ao, aka "nested ao". + * + * Some asynchronous operations are very long-running. Generally, + * since an ao has a gc, any allocations made in that ao will live + * until the ao is completed. When this is not desirable, these + * functions may be used to manage a "sub-ao". + * + * The returned sub-ao is suitable for passing to gc-related functions + * and macros such as libxl__ao_inprogress_gc, AO_GC, and STATE_AO_GC. + * + * It MUST NOT be used with AO_INPROGRESS, AO_ABORT, + * libxl__ao_complete, libxl__ao_progress_report, and so on. + * + * The caller must ensure that all of the sub-ao''s are freed before + * the parent is. Multiple levels of nesting are OK (although + * hopefully they won''t be necessary). + */ + +_hidden libxl__ao *libxl__nested_ao_create(libxl__ao *parent); /* cannot fail */ +_hidden void libxl__nested_ao_free(libxl__ao *child); + + +/* * File descriptors and CLOEXEC */ -- 1.7.10.4
Ian Campbell
2013-Nov-12 15:50 UTC
Re: [PATCH v2] libxl: Introduce nested async operations (nested ao)
On Tue, 2013-11-12 at 15:34 +0000, Ian Jackson wrote:> Roger Pau Monne writes ("[PATCH v2 01/10] libxl: Introduce nested async operations (nested ao)"): > > This allows a long-running ao to avoid accumulating memory. Each > > nested ao has its own gc. > > Thanks. Ian C wanted an improved comment, so: > > From: Ian Jackson <ian.jackson@eu.citrix.com> > Date: Mon, 4 Nov 2013 17:56:15 +0000 > Subject: [PATCH] libxl: Introduce nested async operations (nested ao) > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8 > Content-Transfer-Encoding: 8bit > > This allows a long-running ao to avoid accumulating memory. Each > nested ao has its own gc. > > Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com> > Cc: Roger Pau Monné <roger.pau@citrix.com>Acked-by: Ian Campbell <ian.campbell@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Ian Jackson
2013-Nov-12 16:35 UTC
Re: [PATCH v2] libxl: Introduce nested async operations (nested ao)
Ian Campbell writes ("Re: [PATCH v2] libxl: Introduce nested async operations (nested ao)"):> On Tue, 2013-11-12 at 15:34 +0000, Ian Jackson wrote: > > Roger Pau Monne writes ("[PATCH v2 01/10] libxl: Introduce nested async operations (nested ao)"):...> > This allows a long-running ao to avoid accumulating memory. Each > > nested ao has its own gc.Thanks, I have applied this with your acks. Ian.