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Tue, 28 Jan 2020 07:58:02 -0800 (PST) Date: Tue, 28 Jan 2020 16:58:00 +0100 From: Corentin Labbe To: Horia Geanta 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-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200128_075804_602136_E86B9BDE X-CRM114-Status: GOOD ( 13.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "herbert@gondor.apana.org.au" , Iuliana Prodan , "linux-sunxi@googlegroups.com" , "mripard@kernel.org" , "linux-kernel@vger.kernel.org" , "wens@csie.org" , "linux-crypto@vger.kernel.org" , "davem@davemloft.net" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.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. 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