linux-kernel - Re: [PATCH RESEND 6.5.y] mm/damon/sysfs: check DAMOS regions update progress from before

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Message-ID: <2023103157-rebuttal-directed-7f83@gregkh>
Date:   Tue, 31 Oct 2023 12:16:06 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     SeongJae Park <sj@...nel.org>
Cc:     stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
        damon@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 6.5.y] mm/damon/sysfs: check DAMOS regions update
 progress from before_terminate()

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@...nel.org>
> Cc: <stable@...r.kernel.org>	[6.2.x]
> Signed-off-by: Andrew Morton <akpm@...ux-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