Re: [PATCH] fix locking in cpu_disable_scheduler()

[George Dunlap <george.dunlap@eu.citrix.com>]

On 10/28/2013 04:05 PM, Jan Beulich wrote:
> So commit eedd6039 ("scheduler: adjust internal locking interface")
> uncovered - by now using proper spin lock constructs - a bug after all:
> When bringing down a CPU, cpu_disable_scheduler() gets called with
> interrupts disabled, and hence the use of vcpu_schedule_lock_irq() was
> never really correct (i.e. the caller ended up with interrupts enabled
> despite having disabled them explicitly).
>
> Fixing this however surfaced another problem: The call path
> vcpu_migrate() -> evtchn_move_pirqs() wants to acquire the event lock,
> which however is a non-IRQ-safe once, and hence check_lock() doesn't
> like this lock to be acquired when interrupts are already off. As we're
> in stop-machine context here, getting things wrong wrt interrupt state
> management during lock acquire/release is out of question though, so
> the simple solution to this appears to be to just suppress spin lock
> debugging for the period of time while the stop machine callback gets
> run.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: George Dunlap <george.dunlap@eu.citrix.com>