Commit 1f25c172f837 ("monitor: use aio_co_reschedule_self()") was a code
cleanup that uses aio_co_reschedule_self() instead of open coding
coroutine rescheduling.

Bug RHEL-34618 was reported and Kevin Wolf <kwolf@redhat.com> identified
the root cause. I missed that aio_co_reschedule_self() ->
qemu_get_current_aio_context() only knows about
qemu_aio_context/IOThread AioContexts and not about iohandler_ctx. It
does not function correctly when going back from the iohandler_ctx to
qemu_aio_context.

Go back to open coding the AioContext transitions to avoid this bug.

This reverts commit 1f25c172f83704e350c0829438d832384084a74d.

Buglink: https://issues.redhat.com/browse/RHEL-34618
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qapi/qmp-dispatch.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index f3488afeef..176b549473 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -212,7 +212,8 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommandList *cmds, QObject *requ
              * executing the command handler so that it can make progress if it
              * involves an AIO_WAIT_WHILE().
              */
-            aio_co_reschedule_self(qemu_get_aio_context());
+            aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self());
+            qemu_coroutine_yield();
         }
 
         monitor_set_cur(qemu_coroutine_self(), cur_mon);
@@ -226,7 +227,9 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommandList *cmds, QObject *requ
              * Move back to iohandler_ctx so that nested event loops for
              * qemu_aio_context don't start new monitor commands.
              */
-            aio_co_reschedule_self(iohandler_get_aio_context());
+            aio_co_schedule(iohandler_get_aio_context(),
+                            qemu_coroutine_self());
+            qemu_coroutine_yield();
         }
     } else {
        /*
-- 
2.45.0

CC-ing stable since 1f25c172f83704e350c0829438d832384084a74d is in 9.0.0

Am 06.05.24 um 21:06 schrieb Stefan Hajnoczi:
> Commit 1f25c172f837 ("monitor: use aio_co_reschedule_self()") was a code
> cleanup that uses aio_co_reschedule_self() instead of open coding
> coroutine rescheduling.
> 
> Bug RHEL-34618 was reported and Kevin Wolf <kwolf@redhat.com> identified
> the root cause. I missed that aio_co_reschedule_self() ->
> qemu_get_current_aio_context() only knows about
> qemu_aio_context/IOThread AioContexts and not about iohandler_ctx. It
> does not function correctly when going back from the iohandler_ctx to
> qemu_aio_context.
> 
> Go back to open coding the AioContext transitions to avoid this bug.
> 
> This reverts commit 1f25c172f83704e350c0829438d832384084a74d.
> 
> Buglink: https://issues.redhat.com/browse/RHEL-34618
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  qapi/qmp-dispatch.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
> index f3488afeef..176b549473 100644
> --- a/qapi/qmp-dispatch.c
> +++ b/qapi/qmp-dispatch.c
> @@ -212,7 +212,8 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommandList *cmds, QObject *requ
>               * executing the command handler so that it can make progress if it
>               * involves an AIO_WAIT_WHILE().
>               */
> -            aio_co_reschedule_self(qemu_get_aio_context());
> +            aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self());
> +            qemu_coroutine_yield();
>          }
>  
>          monitor_set_cur(qemu_coroutine_self(), cur_mon);
> @@ -226,7 +227,9 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommandList *cmds, QObject *requ
>               * Move back to iohandler_ctx so that nested event loops for
>               * qemu_aio_context don't start new monitor commands.
>               */
> -            aio_co_reschedule_self(iohandler_get_aio_context());
> +            aio_co_schedule(iohandler_get_aio_context(),
> +                            qemu_coroutine_self());
> +            qemu_coroutine_yield();
>          }
>      } else {
>         /*

Am 29.05.2024 um 12:33 hat Fiona Ebner geschrieben:
> CC-ing stable since 1f25c172f83704e350c0829438d832384084a74d is in 9.0.0

Good point, I'm also updating the commit message in my tree to add
a Cc: line. Thanks for catching this, Fiona!

Kevin