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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2024-02-06 14:06:10 -0500 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2024-02-07 14:44:21 +0100 |
| commit | 1f25c172f83704e350c0829438d832384084a74d (patch) | |
| tree | 4fa82d83400f8fe6a367bbf580048fe250794a3f | |
| parent | 8802f4f4e3a3e7e0ffc778cab853b14349574a7b (diff) | |
| download | qemu-1f25c172f83704e350c0829438d832384084a74d.zip qemu-1f25c172f83704e350c0829438d832384084a74d.tar.gz qemu-1f25c172f83704e350c0829438d832384084a74d.tar.bz2 | |
monitor: use aio_co_reschedule_self()
The aio_co_reschedule_self() API is designed to avoid the race
condition between scheduling the coroutine in another AioContext and
yielding.
The QMP dispatch code uses the open-coded version that appears
susceptible to the race condition at first glance:
aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self());
qemu_coroutine_yield();
The code is actually safe because the iohandler and qemu_aio_context
AioContext run under the Big QEMU Lock. Nevertheless, set a good example
and use aio_co_reschedule_self() so it's obvious that there is no race.
Suggested-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240206190610.107963-6-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
| -rw-r--r-- | qapi/qmp-dispatch.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c index 176b549..f3488af 100644 --- a/qapi/qmp-dispatch.c +++ b/qapi/qmp-dispatch.c @@ -212,8 +212,7 @@ 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_schedule(qemu_get_aio_context(), qemu_coroutine_self()); - qemu_coroutine_yield(); + aio_co_reschedule_self(qemu_get_aio_context()); } monitor_set_cur(qemu_coroutine_self(), cur_mon); @@ -227,9 +226,7 @@ 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_schedule(iohandler_get_aio_context(), - qemu_coroutine_self()); - qemu_coroutine_yield(); + aio_co_reschedule_self(iohandler_get_aio_context()); } } else { /* |