From: Rusty Russell <rusty@rustcorp.com.au>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
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
Cc: sbw@mit.edu, tj@kernel.org, amit.kucheria@linaro.org,
rostedt@goodmis.org, rjw@sisk.pl,
srivatsa.bhat@linux.vnet.ibm.com, 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 10:09:22 +1030 [thread overview]
Message-ID: <87obi9gzf9.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20121204085419.25919.79543.stgit@srivatsabhat.in.ibm.com>
"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".
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).
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 ;)
Rusty.
next prev parent reply other threads:[~2012-12-04 23:42 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 [this message]
2012-12-05 12:44 ` Srivatsa S. Bhat
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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