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Tue, 28 Jan 2020 07:58:03 -0800 (PST) Received: from Red ([2a01:cb1d:3d5:a100:2e56:dcff:fed2:c6d6]) by smtp.googlemail.com with ESMTPSA id i8sm26328713wro.47.2020.01.28.07.58.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jan 2020 07:58:02 -0800 (PST) Date: Tue, 28 Jan 2020 16:58:00 +0100 From: Corentin Labbe To: Horia Geanta Cc: "davem@davemloft.net" , "herbert@gondor.apana.org.au" , "mripard@kernel.org" , "wens@csie.org" , Iuliana Prodan , "linux-sunxi@googlegroups.com" , "linux-crypto@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/9] crypto: engine: workqueue can only be processed one by one Message-ID: <20200128155800.GB17295@Red> References: <20200122104528.30084-1-clabbe.montjoie@gmail.com> <20200122104528.30084-2-clabbe.montjoie@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 28, 2020 at 03:50:14PM +0000, Horia Geanta wrote: > On 1/22/2020 12:46 PM, Corentin Labbe wrote: > > Some bykeshedding are unnecessary since a workqueue can only be executed > > one by one. > > This behaviour is documented in: > > - kernel/kthread.c: comment of kthread_worker_fn() > > - Documentation/core-api/workqueue.rst: the functions associated with the work items one after the other > [...] > > @@ -73,16 +73,6 @@ static void crypto_pump_requests(struct crypto_engine *engine, > > > > spin_lock_irqsave(&engine->queue_lock, flags); > > > > - /* Make sure we are not already running a request */ > > - if (engine->cur_req) > > - goto out; > > - > This check is here for a good reason, namely because crypto engine > cannot currently handle multiple crypto requests being in "flight" > in parallel. > > More exactly, if this check is removed the following sequence could occur: > crypto_pump_work() -> crypto_pump_requests() -> .do_one_request(areq1) > crypto_pump_work() -> crypto_pump_requests() -> .do_one_request(areq2) > crypto_finalize_request(areq1) > crypto_finalize_request(areq2) > As explained in the commitlog, crypto_pump_work() cannot be ran twice. Regards