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bh=eX14L0szIJbf5c1V1hIwg1QL4t2eiWi0Bn+lvuojEGM=; b=aUyL4yo4g0T0m1EQ6fzNBzUfkd+fUT/aApHUtUHPpblEw94A6gfgDa0y2ALe3GIJxOsTec TKHMvsRKEwcdBT3urlCS5kVqCwAUM7BGoc66tmkKcczl2Dk97k7foIRFh9N43DnsAU1o18 3ITOhi+6W+RnGeXwOSH6WfJsDv9QfiA= X-MC-Unique: ApyfVsc3NrOAQU8qmjxpyA-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 05/16] monitor: use aio_co_reschedule_self() Date: Wed, 7 Feb 2024 22:55:55 +0100 Message-ID: <20240207215606.206038-6-kwolf@redhat.com> In-Reply-To: <20240207215606.206038-1-kwolf@redhat.com> References: <20240207215606.206038-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.106, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1707343094160100001 Content-Type: text/plain; charset="utf-8" From: Stefan Hajnoczi 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 Reviewed-by: Manos Pitsidianakis Reviewed-by: Hanna Czenczek Signed-off-by: Stefan Hajnoczi Message-ID: <20240206190610.107963-6-stefanha@redhat.com> Reviewed-by: Kevin Wolf Acked-by: Markus Armbruster Reviewed-by: Michael S. Tsirkin Signed-off-by: Kevin Wolf --- 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 QmpCommand= List *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()); } =20 monitor_set_cur(qemu_coroutine_self(), cur_mon); @@ -227,9 +226,7 @@ QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommand= List *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 { /* --=20 2.43.0