On 6/20/2011 4:05 PM, Russell King - ARM Linux wrote:BTW, how is ARM different from X86 here. I mean the X86 code seems toOn Mon, Jun 20, 2011 at 03:58:03PM +0530, Santosh Shilimkar wrote:Why is that ?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 LinuxScheduler uses the active mask and not online mask. For schedules CPU
On Mon, Jun 20, 2011 at 02:53:59PM +0530, Santosh Shilimkar wrote:The current ARM CPU hotplug code suffers from couple of race
in CPU online path with scheduler.
The ARM CPU hotplug code doesn't wait for hot-plugged CPU to be
active as part of cpu_notify() by the CPU which brought it up before
Hmm, why not just move the set_cpu_online() call before
and add the wait after the set_cpu_online() ?
Actually, the race is caused by the CPU being marked online (and
available for the scheduler) but not yet active (the CPU asking this
to boot hasn't run the online notifiers yet.)
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 toNo it doesn't work. I still get the crash. The important point
processes scheduled on it (because migration is not initialized)
shouldn't be scheduling processes on the new CPU yet.
In any case, this should close the window by ensuring that we don't
an interrupt in the online-but-not-active case. Can you please test?
here is not to enable interrupts before CPU is marked
as online and active.
But we can't do that.
Is it because of calibration or the hotplug start notifies needs to
be called with interrupts enabled ?