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Date:   Tue, 31 Oct 2023 12:16:06 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     SeongJae Park <sj@kernel.org>
Cc:     stable@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        damon@lists.linux.dev, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND 6.5.y] mm/damon/sysfs: check DAMOS regions update
 progress from before_terminate()
Message-ID: <2023103157-rebuttal-directed-7f83@gregkh>
References: <2023102716-prudishly-reggae-1b29@gregkh>
 <20231028213936.45621-1-sj@kernel.org>
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On Sat, Oct 28, 2023 at 09:39:36PM +0000, SeongJae Park wrote:
> DAMON_SYSFS can receive DAMOS tried regions update request while kdamond
> is already out of the main loop and before_terminate callback
> (damon_sysfs_before_terminate() in this case) is not yet called.  And
> damon_sysfs_handle_cmd() can further be finished before the callback is
> invoked.  Then, damon_sysfs_before_terminate() unlocks damon_sysfs_lock,
> which is not locked by anyone.  This happens because the callback function
> assumes damon_sysfs_cmd_request_callback() should be called before it.
> Check if the assumption was true before doing the unlock, to avoid this
> problem.
> 
> Link: https://lkml.kernel.org/r/20231007200432.3110-1-sj@kernel.org
> Fixes: f1d13cacabe1 ("mm/damon/sysfs: implement DAMOS tried regions update command")
> Signed-off-by: SeongJae Park <sj@kernel.org>
> Cc: <stable@vger.kernel.org>	[6.2.x]
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> (cherry picked from commit 76b7069bcc89dec33f03eb08abee165d0306b754)
> ---
> 
> I sent this patch yesterday, but seems not archived in lore.kernel.org.
> Sending again Cc-ing more mailing lists, to ensure it is sent and others can
> find it, to avoid any duplicated works.

Now queued up, thanks.

greg k-h