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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1r0lTo-00217a-9G; Wed, 08 Nov 2023 16:32:36 +0000 Date: Wed, 8 Nov 2023 16:32:36 +0000 From: Matthew Wilcox To: Miquel Raynal Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, rostedt@goodmis.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com, Vignesh Raghavendra , Kyungmin Park , Tudor Ambarus , Pratyush Yadav Subject: Re: [RFC PATCH 82/86] treewide: mtd: remove cond_resched() Message-ID: References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107230822.371443-1-ankur.a.arora@oracle.com> <20231107230822.371443-26-ankur.a.arora@oracle.com> <20231108172827.1fc0bd89@xps-13> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20231108172827.1fc0bd89@xps-13> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D3E4FA002D X-Stat-Signature: tdqrkkef3cktcd5mee8qb396jqirrdhy X-HE-Tag: 1699461173-251022 X-HE-Meta: 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 qswyuOJV jhVIxEGti/LZB0mZRszk4K0tSuiknCvEvbPceQWZ3GObPt/RczTEvmhfxZ2eMx95CkU+Ra+YxvOAg1/7le7Tks9shwTmjLaDu9E/igDSdCDdmy7+3sBv6kKy4IZ29ohBJHkrOjSKxmGzCULJY5u+KiII9zQc+P9FImbhZJ/WLZ2Qg1ybjm9/VV44tiA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Nov 08, 2023 at 05:28:27PM +0100, Miquel Raynal wrote: > > --- a/drivers/mtd/nand/raw/nand_legacy.c > > +++ b/drivers/mtd/nand/raw/nand_legacy.c > > @@ -203,7 +203,13 @@ void nand_wait_ready(struct nand_chip *chip) > > do { > > if (chip->legacy.dev_ready(chip)) > > return; > > - cond_resched(); > > + /* > > + * Use a cond_resched_stall() to avoid spinning in > > + * a tight loop. > > + * Though, given that the timeout is in milliseconds, > > + * maybe this should timeout or event wait? > > Event waiting is precisely what we do here, with the hardware access > which are available in this case. So I believe this part of the comment > (in general) is not relevant. Now regarding the timeout I believe it is > closer to the second than the millisecond, so timeout-ing is not > relevant either in most cases (talking about mtd/ in general). I think you've misunderstood what Ankur wrote here. What you're currently doing is spinning in a very tight loop. The comment is suggesting you might want to msleep(1) or something to avoid burning CPU cycles. It'd be even better if the hardware could signal you somehow, but I bet it can't. > > + */ > > + cond_resched_stall(); > > } while (time_before(jiffies, timeo)); > > Thanks, > Miquèl >