From: Peter Zijlstra <peterz@infradead.org>
To: James Morse <james.morse@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: get_online_cpus() from a preemptible() context (bug?)
Date: Mon, 6 Nov 2017 11:40:38 +0100 [thread overview]
Message-ID: <20171106104038.GD3857@worktop> (raw)
In-Reply-To: <20171106103212.GG3165@worktop.lehotels.local>
On Mon, Nov 06, 2017 at 11:32:12AM +0100, Peter Zijlstra wrote:
> On Fri, Nov 03, 2017 at 02:45:45PM +0000, James Morse wrote:
> > Hi Thomas, Peter,
> >
> > I'm trying to work out what stops a thread being pre-empted and migrated between
> > calling get_online_cpus() and put_online_cpus().
Nothing; why would you think it would? All those functions guarantee is
that any CPU observed as being online says online (and its converse,
that a CPU observed as being offline, says offline, although less people
care about that one).
That is; it serializes against CPU hotplug, nothing else.
next prev parent reply other threads:[~2017-11-06 10:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-03 14:45 get_online_cpus() from a preemptible() context (bug?) James Morse
2017-11-06 10:32 ` Peter Zijlstra
2017-11-06 10:40 ` Peter Zijlstra [this message]
2017-11-06 18:51 ` James Morse
2017-11-06 21:07 ` Peter Zijlstra
2017-11-08 16:07 ` James Morse
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