[PATCH] qmp: fix aio_poll() assertion failure on Windows

[PATCH] qmp: fix aio_poll() assertion failure on Windows

[Volker Rümelin]

Commit 9ce44e2ce2 "qmp: Move dispatcher to a coroutine" modified
aio_poll() in util/aio-posix.c to avoid an assertion failure. This
change is missing in util/aio-win32.c.

Apply the changes to util/aio-posix.c to util/aio-win32.c too.
This fixes an assertion failure on Windows whenever QEMU exits.

$ ./qemu-system-x86_64.exe -machine pc,accel=tcg -display gtk
**
ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion failed:
(in_aio_context_home_thread(ctx))
Bail out! ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion
failed: (in_aio_context_home_thread(ctx))

Fixes: 9ce44e2ce2 ("qmp: Move dispatcher to a coroutine")
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
---
 util/aio-win32.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/util/aio-win32.c b/util/aio-win32.c
index e7b1d649e9..168717b51b 100644
--- a/util/aio-win32.c
+++ b/util/aio-win32.c
@@ -18,6 +18,7 @@
 #include "qemu/osdep.h"
 #include "qemu-common.h"
 #include "block/block.h"
+#include "qemu/main-loop.h"
 #include "qemu/queue.h"
 #include "qemu/sockets.h"
 #include "qapi/error.h"
@@ -333,8 +334,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
      * There cannot be two concurrent aio_poll calls for the same AioContext (or
      * an aio_poll concurrent with a GSource prepare/check/dispatch callback).
      * We rely on this below to avoid slow locked accesses to ctx->notify_me.
+     *
+     * aio_poll() may only be called in the AioContext's thread. iohandler_ctx
+     * is special in that it runs in the main thread, but that thread's context
+     * is qemu_aio_context.
      */
-    assert(in_aio_context_home_thread(ctx));
+    assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ?
+                                      qemu_get_aio_context() : ctx));
     progress = false;
 
     /* aio_notify can avoid the expensive event_notifier_set if
-- 
2.26.2

Re: [PATCH] qmp: fix aio_poll() assertion failure on Windows

[Stefan Hajnoczi]

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On Wed, Oct 21, 2020 at 08:40:33AM +0200, Volker Rümelin wrote:
> Commit 9ce44e2ce2 "qmp: Move dispatcher to a coroutine" modified
> aio_poll() in util/aio-posix.c to avoid an assertion failure. This
> change is missing in util/aio-win32.c.
> 
> Apply the changes to util/aio-posix.c to util/aio-win32.c too.
> This fixes an assertion failure on Windows whenever QEMU exits.
> 
> $ ./qemu-system-x86_64.exe -machine pc,accel=tcg -display gtk
> **
> ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion failed:
> (in_aio_context_home_thread(ctx))
> Bail out! ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion
> failed: (in_aio_context_home_thread(ctx))
> 
> Fixes: 9ce44e2ce2 ("qmp: Move dispatcher to a coroutine")
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
> ---
>  util/aio-win32.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)

Thanks, applied to my block-next tree:
https://gitlab.com/stefanha/qemu/commits/block-next

Stefan

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Re: [PATCH] qmp: fix aio_poll() assertion failure on Windows

[Mark Cave-Ayland]

On 21/10/2020 07:40, Volker Rümelin wrote:

> Commit 9ce44e2ce2 "qmp: Move dispatcher to a coroutine" modified
> aio_poll() in util/aio-posix.c to avoid an assertion failure. This
> change is missing in util/aio-win32.c.
> 
> Apply the changes to util/aio-posix.c to util/aio-win32.c too.
> This fixes an assertion failure on Windows whenever QEMU exits.
> 
> $ ./qemu-system-x86_64.exe -machine pc,accel=tcg -display gtk
> **
> ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion failed:
> (in_aio_context_home_thread(ctx))
> Bail out! ERROR:../qemu/util/aio-win32.c:337:aio_poll: assertion
> failed: (in_aio_context_home_thread(ctx))
> 
> Fixes: 9ce44e2ce2 ("qmp: Move dispatcher to a coroutine")
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
> ---
>   util/aio-win32.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/util/aio-win32.c b/util/aio-win32.c
> index e7b1d649e9..168717b51b 100644
> --- a/util/aio-win32.c
> +++ b/util/aio-win32.c
> @@ -18,6 +18,7 @@
>   #include "qemu/osdep.h"
>   #include "qemu-common.h"
>   #include "block/block.h"
> +#include "qemu/main-loop.h"
>   #include "qemu/queue.h"
>   #include "qemu/sockets.h"
>   #include "qapi/error.h"
> @@ -333,8 +334,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
>        * There cannot be two concurrent aio_poll calls for the same AioContext (or
>        * an aio_poll concurrent with a GSource prepare/check/dispatch callback).
>        * We rely on this below to avoid slow locked accesses to ctx->notify_me.
> +     *
> +     * aio_poll() may only be called in the AioContext's thread. iohandler_ctx
> +     * is special in that it runs in the main thread, but that thread's context
> +     * is qemu_aio_context.
>        */
> -    assert(in_aio_context_home_thread(ctx));
> +    assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ?
> +                                      qemu_get_aio_context() : ctx));
>       progress = false;
>   
>       /* aio_notify can avoid the expensive event_notifier_set if

Sorry about the delay, however I've just tried this on top of git master and it fixes 
the problem with the assert() when exiting QEMU on Win32 so:

Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

Is it possible to get this merged for 5.2?


ATB,

Mark.