From: Andrew Morton <akpm@linux-foundation.org>
To: Shakeel Butt <shakeelb@google.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH v2] percpu_counter: add percpu_counter_sum_all interface
Date: Tue, 8 Nov 2022 17:26:03 -0800 [thread overview]
Message-ID: <20221108172603.8d547faa8f0cf0c340fd7150@linux-foundation.org> (raw)
In-Reply-To: <20221109012011.881058-1-shakeelb@google.com>
On Wed, 9 Nov 2022 01:20:11 +0000 Shakeel Butt <shakeelb@google.com> wrote:
> However there is a small race window between the online CPUs traversal
> of percpu_counter_sum and the CPU offline callback. The offline callback
> has to traverse all the percpu_counters on the system to flush the CPU
> local data which can be a lot. During that time, the CPU which is going
> offline has already been published as offline to all the readers. So, as
> the offline callback is running, percpu_counter_sum can be called for
> one counter which has some state on the CPU going offline. Since
> percpu_counter_sum only traverses online CPUs, it will skip that
> specific CPU and the offline callback might not have flushed the state
> for that specific percpu_counter on that offlined CPU.
LGTM.
What are the user-visible effects of this bug? Should we cc:stable? If
so, can you identify a suitable Fixes:?
Thanks.
next prev parent reply other threads:[~2022-11-09 1:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-09 1:20 Shakeel Butt
2022-11-09 1:26 ` Andrew Morton [this message]
2022-11-09 1:29 ` Shakeel Butt
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