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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id a6sm3682399wmm.0.2021.03.17.10.19.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Mar 2021 10:19:59 -0700 (PDT) Subject: Re: [PATCH 4/6] coroutine-lock: reimplement CoRwLock to fix downgrade bug To: David Edmondson , qemu-devel@nongnu.org References: <20210317121641.215714-1-pbonzini@redhat.com> <20210317121641.215714-5-pbonzini@redhat.com> From: Paolo Bonzini Message-ID: <3146529c-788a-2d64-0369-cb6f28be2151@redhat.com> Date: Wed, 17 Mar 2021 18:19:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, 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, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17/03/21 16:17, David Edmondson wrote: >> + if (tkt) { >> + if (tkt->read) { >> + if (lock->owners >= 0) { >> + lock->owners++; >> + co = tkt->co; >> + } >> + } else { >> + if (lock->owners == 0) { >> + lock->owners = -1; >> + co = tkt->co; >> + } >> + } >> + } >> + >> + if (co) { >> + QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next); >> + qemu_co_mutex_unlock(&lock->mutex); >> + aio_co_wake(co); >> + } else { >> + qemu_co_mutex_unlock(&lock->mutex); >> + } > > This block could be pushed up into the earlier block, but I imagine that > the compiler will do it for you. I guess I could do if (!tkt || (tkt->read ? lock->owners < 0 : lock->owners != 0)) { qemu_co_mutex_unlock(&lock->mutex); return; } if (tkt->read) { lock->owners++; } else { lock->owners = -1; } co = tkt->co; QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next); qemu_co_mutex_unlock(&lock->mutex); aio_co_wake(co); but I find it less readable. So that leaves only the of/or typo, right? Paolo