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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id q4sm6267465ejx.8.2021.01.23.14.13.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 23 Jan 2021 14:13:11 -0800 (PST) To: Laszlo Ersek , Max Reitz , qemu-devel@nongnu.org References: <20210122102041.27031-1-mreitz@redhat.com> <1121a803-98e7-6d41-119c-3d82717976ec@redhat.com> From: Paolo Bonzini Subject: Re: [PATCH] coroutine-sigaltstack: Keep SIGUSR2 handler up Message-ID: <063dd2a6-a3ae-0d7c-3e29-96a08a6d9a3d@redhat.com> Date: Sat, 23 Jan 2021 23:13:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 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: 8bit Received-SPF: pass client-ip=63.128.21.124; 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=-0.165, 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_H4=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: Kevin Wolf , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 22/01/21 22:26, Laszlo Ersek wrote: > That seems bogus, per POSIX, given that all signals except SIGUSR2 are > included in the mask passed to sigsuspend(). What happens if you get a SIGSTOP at exactly the wrong time? (Yeah I know how incredibly unlikely that would be). BTW if we are in a mood for cleanup, there's no reason to use pthread_key_t instead of __thread + qemu_thread_atexit_add (adding a Notifier to struct CoroutineThreadState). That would fix the issue with async-signal safety of pthread_getspecific. (It makes sense for the function not to be async-signal safe since it can in principle allocate memory for the data. In practice it's most likely okay if the function has been called before on this thread). Paolo