From: "Ильфат Гаптрахманов" <i.gaptrakhmanov@rosalinux.ru>
To: "Matthew Wilcox" <willy@infradead.org>,
"Михаил Новоселов" <m.novosyolov@rosalinux.ru>
Cc: riel@surriel.com, mgorman@techsingularity.net,
peterz@infradead.org, mingo@kernel.org,
akpm@linux-foundation.org, stable@vger.kernel.org,
sashal@kernel.org, "Бетхер Александр" <a.betkher@rosalinux.ru>
Subject: Re: Serious regression on 6.1.x-stable caused by "bounds: support non-power-of-two CONFIG_NR_CPUS"
Date: Mon, 29 Apr 2024 16:37:43 +0300 [thread overview]
Message-ID: <79ac00a0-4107-bf1a-00c2-07ade9a7791e@rosalinux.ru> (raw)
In-Reply-To: <Zi-P2rrWZTlrpi3B@casper.infradead.org>
29.04.2024 15:17, Matthew Wilcox пишет:
> CONFIG_NR_CPUS=8192
>
> Since you're using a power-of-two, this should have been a no-op.
> But bits_per() doesn't work the way I thought it did!
>
> #define bits_per(n) \
> ( \
> __builtin_constant_p(n) ? ( \
> ((n) == 0 || (n) == 1) \
> ? 1 : ilog2(n) + 1 \
> ) : \
>
> CONFIG_NR_CPUS is obviously a constant, and larger than 1, so we end up
> calling ilog2(n) + 1. So we allocate one extra bit.
>
> I should have changed this to
> DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS - 1))
>
> Can you test that and report back? I'll prepare a fix for mainline in
> the meantime.
Yes, this fix solved the problem
prev parent reply other threads:[~2024-04-29 13:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-28 14:58 Serious regression on 6.1.x-stable caused by "bounds: support non-power-of-two CONFIG_NR_CPUS" Mikhail Novosyolov
2024-04-29 2:56 ` Matthew Wilcox
2024-04-29 4:07 ` Михаил Новоселов
2024-04-29 12:17 ` Matthew Wilcox
2024-04-29 13:37 ` Ильфат Гаптрахманов [this message]
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