linux-kernel - Re: [PATCH next v3 02/15] mtd: mtdoops: synchronize kmsg

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Date:   Mon, 1 Mar 2021 13:13:22 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org
Subject: Re: [PATCH next v3 02/15] mtd: mtdoops: synchronize kmsg_dumper

On Thu 2021-02-25 21:24:25, John Ogness wrote:
> The kmsg_dumper can be called from any context and CPU, possibly
> from multiple CPUs simultaneously. Since the writing of the buffer
> can occur from a later scheduled work queue, the oops buffer must
> be protected against simultaneous dumping.
> 
> Use an atomic bit to mark when the buffer is protected. Release the
> protection in between setting the buffer and the actual writing in
> order for a possible panic (immediate write) to be written during
> the scheduling of a previous oops (delayed write).

Just to be sure. You did not use spin lock to prevent problems
with eventual double unlock in panic(). Do I get it correctly,
please?

> Signed-off-by: John Ogness <john.ogness@...utronix.de>

Anyway, it looks good to me.

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr