From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Yan Zheng <zheng.z.yan@intel.com>,
Stephane Eranian <eranian@google.com>,
Ingo Molnar <mingo@kernel.org>,
Vince Weaver <vincent.weaver@maine.edu>
Subject: Re: Possible race between CPU hotplug and perf_pmu_migrate_context
Date: Fri, 5 Sep 2014 21:54:39 +0200 [thread overview]
Message-ID: <20140905195439.GU4783@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <CA+55aFwqhPLjTyiwVs2F9p8BPxMV=FOTgLpcHcV2rUPvTt71ow@mail.gmail.com>
On Fri, Sep 05, 2014 at 10:31:49AM -0700, Linus Torvalds wrote:
> So quite frankly, the whole perf_pmu_migrate_context() thing looks
> completely and fundamentally broken.
Yes, agreed. We can go play very nasty games, but fundamentally agreed.
> Or even just say: "if somebody takes down a CPU with existing uncore
> events, those events are now effectively dead". Don't try to migrate
> them, don't try to create new events on another CPU, just let it go.
> The CPU is down, the events are inactive.
>
> Keep it simple. Not the current completely broken thing that clearly
> doesn't honor the actual real rules for "event->ctx". Because the
> current rules are effectively that event->ctx is a constant over the
> whole lifetime of the event. Agreed?
I like this best, I've never really been a supporter of hotplug games.
next prev parent reply other threads:[~2014-09-05 19:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-01 18:18 Possible race between CPU hotplug and perf_pmu_migrate_context Mark Rutland
2014-09-01 19:05 ` Peter Zijlstra
2014-09-02 18:58 ` Mark Rutland
2014-09-03 11:50 ` Mark Rutland
2014-09-04 10:44 ` Peter Zijlstra
2014-09-04 11:07 ` Mark Rutland
2014-09-05 15:16 ` Peter Zijlstra
2014-09-05 15:41 ` Linus Torvalds
2014-09-05 16:50 ` Vince Weaver
2014-09-05 16:59 ` Mark Rutland
2014-09-05 17:31 ` Linus Torvalds
2014-09-05 19:54 ` Peter Zijlstra [this message]
2014-09-08 8:39 ` Peter Zijlstra
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