From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Alexey Klimov <aklimov@redhat.com>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
yury.norov@gmail.com, tglx@linutronix.de,
Joshua Baker <jobaker@redhat.com>,
audralmitchel@gmail.com, arnd@arndb.de,
gregkh@linuxfoundation.org, rafael@kernel.org, tj@kernel.org,
Qais Yousef <qais.yousef@arm.com>,
hannes@cmpxchg.org, Alexey Klimov <klimov.linux@gmail.com>
Subject: Re: [PATCH v2] cpu/hotplug: wait for cpuset_hotplug_work to finish on cpu onlining
Date: Thu, 18 Mar 2021 15:12:25 -0400 [thread overview]
Message-ID: <87a6r0uvhi.fsf@oracle.com> (raw)
In-Reply-To: <CAFBcO+99Ax5MuOtzNx=NrmnUN=+913Sc-DV83ObOi01A=kkN3w@mail.gmail.com>
Alexey Klimov <aklimov@redhat.com> writes:
> The first section of comment seems problematic to me with regards to such move:
>
> * As this needs to hold the cpu maps lock it's impossible
> * to call device_offline() because that ends up calling
> * cpu_down() which takes cpu maps lock. cpu maps lock
> * needs to be held as this might race against in kernel
> * abusers of the hotplug machinery (thermal management).
>
> Cpu maps lock is released in cpu_maps_update_done() hence we will move
> dev->offline out of cpu maps lock. Maybe I misunderstood the comment
> and it relates to calling cpu_down_maps_locked() under lock to avoid
> race?
Yes, that's what I take from the comment, the cpu maps lock protects
against racing hotplug operations.
next prev parent reply other threads:[~2021-03-18 19:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-12 0:30 Alexey Klimov
2021-02-12 19:41 ` Daniel Jordan
2021-03-16 3:15 ` Alexey Klimov
2021-03-18 19:12 ` Daniel Jordan [this message]
2021-02-16 18:29 ` Qais Yousef
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