From: Stefan Hajnoczi <stefanha@redhat.com>
To: qemu-devel@nongnu.org
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
Michael Roth <michael.roth@amd.com>,
Kevin Wolf <kwolf@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
Hanna Reitz <hreitz@redhat.com>,
qemu-block@nongnu.org,
Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Subject: [PATCH v2 5/5] monitor: use aio_co_reschedule_self()
Date: Tue, 6 Feb 2024 14:06:10 -0500 [thread overview]
Message-ID: <20240206190610.107963-6-stefanha@redhat.com> (raw)
In-Reply-To: <20240206190610.107963-1-stefanha@redhat.com>
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>
---
qapi/qmp-dispatch.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 176b549473..f3488afeef 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 {
/*
--
2.43.0
next prev parent reply other threads:[~2024-02-06 19:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-06 19:06 [PATCH v2 0/5] virtio-blk: iothread-vq-mapping cleanups Stefan Hajnoczi
2024-02-06 19:06 ` [PATCH v2 1/5] virtio-blk: enforce iothread-vq-mapping validation Stefan Hajnoczi
2024-02-06 19:06 ` [PATCH v2 2/5] virtio-blk: clarify that there is at least 1 virtqueue Stefan Hajnoczi
2024-02-06 19:06 ` [PATCH v2 3/5] virtio-blk: add vq_rq[] bounds check in virtio_blk_dma_restart_cb() Stefan Hajnoczi
2024-02-06 19:06 ` [PATCH v2 4/5] virtio-blk: declare VirtIOBlock::rq with a type Stefan Hajnoczi
2024-02-06 19:06 ` Stefan Hajnoczi [this message]
2024-05-03 17:33 ` [PATCH v2 5/5] monitor: use aio_co_reschedule_self() Kevin Wolf
2024-05-06 18:09 ` Stefan Hajnoczi
2024-02-06 19:08 ` [PATCH v2 0/5] virtio-blk: iothread-vq-mapping cleanups Michael S. Tsirkin
2024-02-07 13:45 ` Kevin Wolf
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