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(p200300cfd74065ef7c9fa118b826ff5f.dip0.t-ipconnect.de. [2003:cf:d740:65ef:7c9f:a118:b826:ff5f]) by smtp.gmail.com with ESMTPSA id l14-20020a05600c4f0e00b0040fc56712e8sm2293529wmq.17.2024.02.06.07.11.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Feb 2024 07:11:56 -0800 (PST) Message-ID: <9071df4c-d08a-4298-b6fb-a562745773a8@redhat.com> Date: Tue, 6 Feb 2024 16:11:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] monitor: use aio_co_reschedule_self() Content-Language: en-US To: Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Kevin Wolf , "Michael S. Tsirkin" , Michael Roth , Markus Armbruster , qemu-block@nongnu.org References: <20240205172659.476970-1-stefanha@redhat.com> <20240205172659.476970-6-stefanha@redhat.com> From: Hanna Czenczek In-Reply-To: <20240205172659.476970-6-stefanha@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.294, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 05.02.24 18:26, Stefan Hajnoczi wrote: > 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 > Signed-off-by: Stefan Hajnoczi > --- > qapi/qmp-dispatch.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) Reviewed-by: Hanna Czenczek