From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" 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 Message-ID: <50BF41A4.8010709@linux.vnet.ibm.com> References: <20121204085149.25919.29920.stgit@srivatsabhat.in.ibm.com> <20121204085419.25919.79543.stgit@srivatsabhat.in.ibm.com> <87obi9gzf9.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87obi9gzf9.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org To: Rusty Russell 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 List-Id: linux-pm@vger.kernel.org On 12/05/2012 05:09 AM, Rusty Russell wrote: > "Srivatsa S. Bhat" writes: >> From: Michael Wang >> >> 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