On Wed, Nov 13, 2013 at 04:05:56PM +0000, Martin Schwidefsky wrote:
> On Wed, 13 Nov 2013 12:19:09 +0000
> Catalin Marinas <catalin.mari...@arm.com> wrote:
> > On Wed, Nov 13, 2013 at 11:41:43AM +0000, Peter Zijlstra wrote:
> > > On Wed, Nov 13, 2013 at 09:16:13AM +0100, Martin Schwidefsky wrote:
> > > > fire_sched_in_preempt_notifiers(current);
> > > > if (mm)
> > > > @@ -4140,8 +4141,10 @@ void idle_task_exit(void)
> > > >
> > > > BUG_ON(cpu_online(smp_processor_id()));
> > > >
> > > > - if (mm != &init_mm)
> > > > + if (mm != &init_mm) {
> > > > switch_mm(mm, &init_mm, current);
> > > > + finish_switch_mm(&init_mm, current);
> > > > + }
> > > > mmdrop(mm);
> > > > }
> >
> > Here finish_switch_mm() is called in the same context with switch_mm().
> > What we have on ARM via switch_mm() is to check for irqs_disabled() and
> > if yes, defer the actual switching via a flag until the
> > finish_arch_post_lock_switch() hook. But on ARM we only cared about the
> > interrupts being enabled.
>
> The guarantee s390 needs is that the rq-lock is not taken. What I have
> seen with the wait loop in switch_mm is a dead lock because one CPU #0
> was looping in switch_mm to wait for the TLB flush of another CPU #1.
> CPU #1 got an interrupt that tried to wake-up a task which happened to
> be on the run-queue of CPU #0.
I'm not familiar with the s390 code, so how's the waiting done? Is it
part of an on_each_cpu() call (that's what I got from smp_ptlb_all)?
--
Catalin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
