Messages in this thread | | | Date | Mon, 15 Oct 2007 23:21:08 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [RFC] cpuset update_cgroup_cpus_allowed |
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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.
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