On Thu, 28 Jul 2011, Yong Zhang wrote: > On Wed, Jul 27, 2011 at 11:52:18PM +0200, Thomas Gleixner wrote: > > On Tue, 26 Jul 2011, Yong Zhang wrote: > > > > > When reading the code, I'm afraid there is a race between migrate_disable() > > > and cpu hotplug. A scenario will like below: > > > > > > CPU0 CPU1 > > > _cpu_down(); > > > cpu_unplug_begin(); > > > wait_for_completion() > > > sync_unplug_thread(); > > > complete(); > > > race_window? /* > > > * migrate_disable() will > > > * not take effect since > > > * hotplug is in progress > > > */ > > > > Rightfully so. The caller will just block on the cpu_hotplug.lock > > mutex until the unplug operation will be done. > > Yup, just notice the mutex_lock/mutex_unlock in pin_current_cpu(). > > But if the caller block on mutex_lock() then waked up, it's possible > that it's been migrated to another cpu. So in the 'retry' loop, we > should reget hotplug_pcp. Ooops, that was the original plan. I somehow managed to fatfinger that. Good catch. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
