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([2a04:ee41:4:31cb:e591:1e1e:abde:a8f1]) by smtp.gmail.com with ESMTPSA id 5sm7358764qtp.81.2022.02.08.03.42.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Feb 2022 03:42:26 -0800 (PST) Message-ID: <1f3d2562-c355-4295-77b5-088d2ed49023@redhat.com> Date: Tue, 8 Feb 2022 12:42:22 +0100 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 v6 00/33] block layer: split block APIs in global state and I/O To: Kevin Wolf References: <20220121170544.2049944-1-eesposit@redhat.com> From: Emanuele Giuseppe Esposito In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eesposit@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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=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: , Cc: Fam Zheng , qemu-devel@nongnu.org, "Denis V. Lunev" , Eric Blake , qemu-block@nongnu.org, Juan Quintela , Daniel Henrique Barboza , Markus Armbruster , Richard Henderson , Greg Kurz , "Dr. David Alan Gilbert" , =?UTF-8?Q?C=c3=a9dric_Le_Goater?= , Stefan Hajnoczi , John Snow , David Gibson , Eduardo Habkost , Vladimir Sementsov-Ogievskiy , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Hanna Reitz , qemu-ppc@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 07/02/2022 19:30, Kevin Wolf wrote: > Am 21.01.2022 um 18:05 hat Emanuele Giuseppe Esposito geschrieben: >> Each function in the GS API will have an assertion, checking >> that it is always running under BQL. >> I/O functions are instead thread safe (or so should be), meaning >> that they *can* run under BQL, but also in an iothread in another >> AioContext. Therefore they do not provide any assertion, and >> need to be audited manually to verify the correctness. > > I wonder if we could actually do something to catch at least some kinds > of bugs. The first conclusion from thinking about it is that we probably > shouldn't open-code assert(qemu_in_main_thread()) everywhere, but have a > macro or inline function for each category to be called in each function. > > So an IO_CODE() macro could increase a counter in the coroutine object > (that is decreased again at the end of the function with g_auto), and > then GLOBAL_STATE_CODE() could not only assert that we're holding the > BQL, but also that the counter is still 0, i.e. it is not (indirectly) > called by an I/O function. > > We may want to enable this only in debug builds, but maybe still worth a > thought anyway? I don't understand what is the point of the counter, do you want to use it as a boolean flag? Would a single counter work in a multi-threaded context? Shouldn't we have it per-thread? And why you increase it only in coroutines? Emanuele