On Mon, Jun 20, 2011 at 03:58:03PM +0530, Santosh Shilimkar wrote: > On 6/20/2011 3:44 PM, Russell King - ARM Linux wrote: >> On Mon, Jun 20, 2011 at 10:50:53AM +0100, Russell King - ARM Linux wrote: >>> On Mon, Jun 20, 2011 at 02:53:59PM +0530, Santosh Shilimkar wrote: >>>> The current ARM CPU hotplug code suffers from couple of race conditions >>>> in CPU online path with scheduler. >>>> The ARM CPU hotplug code doesn't wait for hot-plugged CPU to be marked >>>> active as part of cpu_notify() by the CPU which brought it up before >>>> enabling interrupts. >>> >>> Hmm, why not just move the set_cpu_online() call before notify_cpu_starting() >>> and add the wait after the set_cpu_online() ? >> >> Actually, the race is caused by the CPU being marked online (and therefore >> available for the scheduler) but not yet active (the CPU asking this one >> to boot hasn't run the online notifiers yet.) >> > Scheduler uses the active mask and not online mask. For schedules CPU > is ready for migration as soon as it is marked as active and that's > the reason, interrupts should never be enabled before CPU is marked > as active in online path. > >> This, I feel, is a fault of generic code. If the CPU is not ready to have >> processes scheduled on it (because migration is not initialized) then we >> shouldn't be scheduling processes on the new CPU yet. >> >> In any case, this should close the window by ensuring that we don't receive >> an interrupt in the online-but-not-active case. Can you please test? >> > No it doesn't work. I still get the crash. The important point > here is not to enable interrupts before CPU is marked > as online and active. But we can't do that. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
