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dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1699464079; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EwL18HLJNRnGPl2uNPDaSdhCktpPTaPm9Vsvkljk/7A=; b=K9CUdcZd3PntIjk+yFEWMkADe3RWEJQTE6EDkM2QjXBOJDTgPO/ZreaUWq4m1qLo0PgK4k KOhnO+2uSa2V/JqCJBUiV461P9kzzt1/OrgXaXOGh6l5jyQwQEngk5dw/MiMUsI/mWa83F mGEduvlUqC0ElSy2+RbgR3c/hjsRl9M= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by ams.source.kernel.org (Postfix) with ESMTP id 6BA1BB81DF1; Wed, 8 Nov 2023 17:21:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0DBFC433C8; Wed, 8 Nov 2023 17:21:12 +0000 (UTC) Date: Wed, 8 Nov 2023 12:21:16 -0500 From: Steven Rostedt To: Matthew Wilcox Cc: Miquel Raynal , 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, 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: <20231108122116.5e2c11be@gandalf.local.home> In-Reply-To: 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> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7BD2080008 X-Stat-Signature: xiy5mcb77enk1moaa1m86ga1xxyxg6m8 X-HE-Tag: 1699464079-572733 X-HE-Meta: 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 moK6GK8e /lxkXvsstQejgFAtSHYecAsPDF44JlraWB/BtMUufwwCbUprBcuTRNHtXs41nInY4R+xJfjh7VuRpeInExaK5hbu+CSN8CNlTgM40vGFyCIb1/WSpFohgmwUcHIymmw52Z9C9Ahf7UFYeX4yhDc7QgxiNdNvVw06cbJUlARKsJA+W6NtQGaP3dkmIW99ZoLJkG9cLhj9JjzY24wuJCSoHFNMAKl8U74G9CANCLDujmZ1YcncVaPJCIvGRPX5t/5w7yRa1P2ppV3yWE7XvQUTVo59ntAE01SJzLEscgP9j70trr+9WPU4GFzS+HNb0qQhoIdggNnXisaPxO+xb4SFcOSPA3sAqUByOPXij 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, 8 Nov 2023 16:32:36 +0000 Matthew Wilcox wrote: > 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? =20 > >=20 > > 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). =20 >=20 > 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. >=20 Oh how I wish we could bring back the old PREEMPT_RT cpu_chill()... #define cpu_chill() msleep(1) ;-) -- Steve > > > + */ > > > + cond_resched_stall(); > > > } while (time_before(jiffies, timeo)); =20 > >=20 > > Thanks, > > Miqu=C3=A8l > > =20