[Stable-9.0.2,04/22] Revert "monitor: use aio_co_reschedule_self()"

Commit Message

Michael Tokarev July 4, 2024, 9 p.m. UTC

From: Stefan Hajnoczi <[e-mail]>

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 <[e-mail]> 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.

Cc: [e-mail]
Buglink: https://issues.redhat.com/browse/RHEL-34618
Signed-off-by: Stefan Hajnoczi <[e-mail]>
Message-ID: <[e-mail]>
Reviewed-by: Kevin Wolf <[e-mail]>
Signed-off-by: Kevin Wolf <[e-mail]>
(cherry picked from commit 719c6819ed9a9838520fa732f9861918dc693bda)
Signed-off-by: Michael Tokarev <[e-mail]>

Patch

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 {
        /*