linux-kernel - Re: [PATCH RFC v1 1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices

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Message-ID: <1788102040.295765.1643188123063.JavaMail.zimbra@nod.at>
Date:   Wed, 26 Jan 2022 10:08:43 +0100 (CET)
From:   Richard Weinberger <richard@....at>
To:     David Decotigny <decot+git@...gle.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        David Decotigny <ddecotig@...gle.com>
Subject: Re: [PATCH RFC v1 1/1] mtd_blkdevs: avoid soft lockups with some
 mtd/spi devices

David,

----- Ursprüngliche Mail -----
> Von: "David Decotigny" <decot+git@...gle.com>
> An: "linux-kernel" <linux-kernel@...r.kernel.org>
> CC: "Miquel Raynal" <miquel.raynal@...tlin.com>, "richard" <richard@....at>, "Vignesh Raghavendra" <vigneshr@...com>,
> "linux-mtd" <linux-mtd@...ts.infradead.org>, "David Decotigny" <ddecotig@...gle.com>
> Gesendet: Mittwoch, 26. Januar 2022 09:57:35
> Betreff: [PATCH RFC v1 1/1] mtd_blkdevs: avoid soft lockups with some mtd/spi devices

> From: David Decotigny <ddecotig@...gle.com>
> 
> With some spi devices, the heavy cpu usage due to polling the spi
> registers may lead to netdev timeouts, RCU complaints, etc. This can
> be acute in the absence of CONFIG_PREEMPT. This patch allows to give
> enough breathing room to avoid those false positives.

is the problem real or not? From your description it is not clear to me.
Please include lockdep splats and/or hung-task logs in the commit message.

I have no problem with adding a cond_resched() but first we need to
understand the issue a little better.

Thanks,
//richard