linux-kernel - Re: [PATCH] Revert "seqlock: lockdep assert non-preemptibility on seqcount

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Message-ID: <20200819070022.semyxepadnvtmtcr@linutronix.de>
Date:   Wed, 19 Aug 2020 09:00:22 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Valdis Klētnieks <valdis.kletnieks@...edu>,
        Mark Starovoytov <mstarovoitov@...vell.com>,
        Igor Russkikh <irusskikh@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        linux-kernel@...r.kernel.org, mingo@...hat.com, paulmck@...nel.org,
        peterz@...radead.org, rostedt@...dmis.org, tglx@...utronix.de,
        will@...nel.org
Subject: Re: [PATCH] Revert "seqlock: lockdep assert non-preemptibility on
 seqcount_t write"

On 2020-08-18 17:56:49 [-0700], Guenter Roeck wrote:
> Nice catch. FWIW, there is no obvious reason why this would need to be atomic.
> The calling code does not set a lock, meaning there can be two (or more)
> callers entering this code. Weird, especially since the code looks like it
> would actually need a mutex to work correctly. It might be interesting to
> see what happens if there are, say, half a dozen scripts/processes trying
> to read the hwmon attribute introduced by this patch at the same time.

=> https://lkml.kernel.org/r/20200818161439.3dkf6jzp3vuwmvvh@linutronix.de

> Guenter

Sebastian