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Message-ID: <alpine.DEB.0.9999.0710152311180.22383@chino.kir.corp.google.com> Date: Mon, 15 Oct 2007 23:21:08 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Paul Jackson <pj@....com> cc: menage@...gle.com, nickpiggin@...oo.com.au, a.p.zijlstra@...llo.nl, balbir@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org, clg@...ibm.com, ebiederm@...ssion.com, containers@...ts.osdl.org, serue@...ibm.com, svaidy@...ux.vnet.ibm.com, akpm@...ux-foundation.org, xemul@...nvz.org Subject: Re: [RFC] cpuset update_cgroup_cpus_allowed On Mon, 15 Oct 2007, Paul Jackson wrote: > My solution may be worse than that. Because set_cpus_allowed() will > fail if asked to set a non-overlapping cpumask, my solution could never > terminate. If asked to set a cpusets cpus to something that went off > line right then, this I'd guess this code could keep looping forever, > looking for cpumasks that didn't match, and then not noticing that it > was failing to set them so as they would match. > Why can't you just add a helper function to sched.c: void set_hotcpus_allowed(struct task_struct *task, cpumask_t cpumask) { mutex_lock(&sched_hotcpu_mutex); set_cpus_allowed(task, cpumask); mutex_unlock(&sched_hotcpu_mutex); } And then change each task's cpus_allowed via that function instead of set_cpus_allowed() directly? You don't need to worry about making the task->cpuset->cpus_allowed assignment a critical section because common_cpu_mem_hotplug_unplug() will remove any hot-unplugged cpus from each cpuset's cpus_allowed in the hierarchy. Your loop will still need to be reworked so that cgroup_iter_{start,end}() are not reinvoked unnecessarily and you rely only on cgroup_iter_next() returning NULL to determine when you've gone through the entire list. There's no need to go back and check the cpus_allowed of tasks you've already called set_cpus_allowed() on either directly or indirectly via my helper function above. David - 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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