From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: tglx@linutronix.de, peterz@infradead.org,
paulmck@linux.vnet.ibm.com, mingo@kernel.org,
akpm@linux-foundation.org, namhyung@kernel.org,
vincent.guittot@linaro.org, sbw@mit.edu, tj@kernel.org,
amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl,
wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com,
nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 02/10] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly
Date: Wed, 05 Dec 2012 18:14:20 +0530 [thread overview]
Message-ID: <50BF41A4.8010709@linux.vnet.ibm.com> (raw)
In-Reply-To: <87obi9gzf9.fsf@rustcorp.com.au>
On 12/05/2012 05:09 AM, Rusty Russell wrote:
> "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> writes:
>> From: Michael Wang <wangyun@linux.vnet.ibm.com>
>>
>> With stop_machine() gone from the CPU offline path, we can't depend on
>> preempt_disable() to prevent CPUs from going offline from under us.
>
> Minor gripe: I'd prefer this paragraph to use the future rather than
> past tense, like: "Once stop_machine() is gone ... we won't be able to
> depend".
>
Fixed in the new version.
> Since you're not supposed to use the _stable() accessors without calling
> get_online_cpus_stable_atomic(), why not have
> get_online_cpus_stable_atomic() return a pointer to the stable cpumask?
> (Which is otherwise static, at least for debug).
>
We don't have to worry about this now because the new version doesn't
use stable cpumask.
> Might make the patches messier though...
>
> Oh, and I'd love to see actual benchmarks to make sure we've actually
> fixed a problem with this ;)
>
Of course :-) They will follow, once we have a proper implementation
that we are happy with :-)
Regards,
Srivatsa S. Bhat
next prev parent reply other threads:[~2012-12-05 12:45 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-04 8:53 [RFC PATCH 00/10] CPU hotplug: stop_machine()-free CPU hotplug Srivatsa S. Bhat
2012-12-04 8:53 ` [RFC PATCH 01/10] CPU hotplug: Introduce "stable" cpu online mask, for atomic hotplug readers Srivatsa S. Bhat
2012-12-04 15:17 ` Tejun Heo
2012-12-04 21:14 ` Srivatsa S. Bhat
2012-12-04 22:10 ` Andrew Morton
2012-12-05 2:56 ` Michael Wang
2012-12-05 3:28 ` Michael Wang
2012-12-05 12:38 ` Srivatsa S. Bhat
2012-12-04 8:54 ` [RFC PATCH 02/10] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Srivatsa S. Bhat
2012-12-04 22:17 ` Andrew Morton
2012-12-05 12:41 ` Srivatsa S. Bhat
2012-12-04 23:39 ` Rusty Russell
2012-12-05 12:44 ` Srivatsa S. Bhat [this message]
2012-12-04 8:54 ` [RFC PATCH 03/10] smp, cpu hotplug: Fix on_each_cpu_*() " Srivatsa S. Bhat
2012-12-04 8:54 ` [RFC PATCH 04/10] sched, cpu hotplug: Use stable online cpus in try_to_wake_up() & select_task_rq() Srivatsa S. Bhat
2012-12-04 8:55 ` [RFC PATCH 05/10] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Srivatsa S. Bhat
2012-12-04 8:55 ` [RFC PATCH 06/10] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly Srivatsa S. Bhat
2012-12-04 8:55 ` [RFC PATCH 07/10] KVM: VMX: fix invalid cpu passed to smp_call_function_single Srivatsa S. Bhat
2012-12-04 8:55 ` [RFC PATCH 08/10] KVM: VMX: fix memory order between loading vmcs and clearing vmcs Srivatsa S. Bhat
2012-12-04 8:56 ` [RFC PATCH 09/10] KVM: VMX: fix unsyc vmcs status when cpu is going down Srivatsa S. Bhat
2012-12-04 8:56 ` [RFC PATCH 10/10] cpu: No more __stop_machine() in _cpu_down() Srivatsa S. Bhat
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