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authorTejun Heo <tj@kernel.org>2010-06-08 23:40:36 +0400
committerTejun Heo <tj@kernel.org>2010-06-08 23:40:36 +0400
commit3a101d0548e925ab16ca6aaa8cf4f767d322ddb0 (patch)
treeb90d8c5f2efe30fcfa49a00fdea037567c6cd46f /Documentation/email-clients.txt
parent50a323b73069b169385a8ac65633dee837a7d13f (diff)
downloadlinux-3a101d0548e925ab16ca6aaa8cf4f767d322ddb0.tar.xz
sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining
Currently, when a cpu goes down, cpu_active is cleared before CPU_DOWN_PREPARE starts and cpuset configuration is updated from a default priority cpu notifier. When a cpu is coming up, it's set before CPU_ONLINE but cpuset configuration again is updated from the same cpu notifier. For cpu notifiers, this presents an inconsistent state. Threads which a CPU_DOWN_PREPARE notifier expects to be bound to the CPU can be migrated to other cpus because the cpu is no more inactive. Fix it by updating cpu_active in the highest priority cpu notifier and cpuset configuration in the second highest when a cpu is coming up. Down path is updated similarly. This guarantees that all other cpu notifiers see consistent cpu_active and cpuset configuration. cpuset_track_online_cpus() notifier is converted to cpuset_update_active_cpus() which just updates the configuration and now called from cpuset_cpu_[in]active() notifiers registered from sched_init_smp(). If cpuset is disabled, cpuset_update_active_cpus() degenerates into partition_sched_domains() making separate notifier for !CONFIG_CPUSETS unnecessary. This problem is triggered by cmwq. During CPU_DOWN_PREPARE, hotplug callback creates a kthread and kthread_bind()s it to the target cpu, and the thread is expected to run on that cpu. * Ingo's test discovered __cpuinit/exit markups were incorrect. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Menage <menage@google.com>
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