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[109.164.254.58]) by smtp.gmail.com with ESMTPSA id p16-20020a05600c1d9000b003a60ff7c082sm4596608wms.15.2022.08.18.00.46.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Aug 2022 00:46:59 -0700 (PDT) Message-ID: <563d5629-d47a-9682-f5c8-6be2c4806e8c@redhat.com> Date: Thu, 18 Aug 2022 09:46:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v10 18/21] job.c: enable job lock/unlock and remove Aiocontext locks Content-Language: en-US To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Paolo Bonzini , John Snow , Vladimir Sementsov-Ogievskiy , Wen Congyang , Xie Changlong , Markus Armbruster , Stefan Hajnoczi , Fam Zheng , qemu-devel@nongnu.org References: <20220725073855.76049-1-eesposit@redhat.com> <20220725073855.76049-19-eesposit@redhat.com> <43acbcd7-d00f-ee74-df22-314745900f93@redhat.com> From: Emanuele Giuseppe Esposito In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, 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" Am 17/08/2022 um 20:54 schrieb Vladimir Sementsov-Ogievskiy: > On 8/16/22 15:52, Emanuele Giuseppe Esposito wrote: >>>>    } >>>> @@ -501,8 +481,12 @@ void job_unref_locked(Job *job)> >>>> assert(!job->txn); >>>>              if (job->driver->free) { >>>> +            AioContext *aio_context = job->aio_context; >>>>                job_unlock(); >>>> +            /* FIXME: aiocontext lock is required because cb calls >>>> blk_unref */ >>>> +            aio_context_acquire(aio_context); >>>>                job->driver->free(job); >>>> +            aio_context_release(aio_context); >>> So, job_unref_locked() must be called with aio_context not locked, >>> otherwise we dead-lock here? That should be documented in function >>> declaration comment. >>> >>> For example in qemu-img.c in run_block_job() we do exactly that: call >>> job_unref_locked()  inside aio-context lock critical seaction.. >> No, job_unref_locked has also status and refcnt and all the other fields >> that need to be protectd. Only free must be called without job lock held. >> > > I mean, don't we try here to acquire aio_context twice, when we call > job_unref_locked() with aio_context _already_ acquired? > You're right, so why do we need the AioContext lock in qemu-img then? All jobs API don't need it, aio_poll seems not to need it either, and progress API has its own lock. I guess I could remove it? Emanuele