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Date: Tue, 04 Aug 2009 15:35:44 +0800 From: Lai Jiangshan <laijs@...fujitsu.com> To: Oleg Nesterov <oleg@...hat.com> CC: Andrew Morton <akpm@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Rusty Russell <rusty@...tcorp.com.au>, linux-kernel@...r.kernel.org, Li Zefan <lizf@...fujitsu.com>, Miao Xie <miaox@...fujitsu.com>, Paul Menage <menage@...gle.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Gautham R Shenoy <ego@...ibm.com> Subject: Re: [PATCH] cpusets: rework guarantee_online_cpus() to fix deadlock with cpu_down() Oleg Nesterov wrote: > On 08/02, Lai Jiangshan wrote: >> Oleg Nesterov wrote: >> >>> - do NOT scan cs->parent cpusets. If there are no online CPUs in >>> cs->cpus_allowed, we use cpu_online_mask. This is only possible >>> when we are called by cpu_down() hooks, in that case >>> cpuset_track_online_cpus(CPU_DEAD) will fix things later. >>> >> >> We must scan cs->parent cpusets. >> A task is constrained by a cpuset, > > Yes, the task esacpes its cpuset. With or without this patch. > Because cs->cpus_allowed has no online CPUs. > >> it must be constrained >> this cpuset's parent too. > > It will be constained again, after scan_for_empty_cpusets(), no? cpuset_cpus_allowed() is not only used for CPU offline. sched_setaffinity() also uses it. The task will not be constained again. Or I missed something. Lai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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