Messages in this thread Patch in this message |  | | Date | Wed, 13 Nov 2013 17:03:58 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH 1/2] sched/mm: add finish_switch_mm function |
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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.marinas@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
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