Quoting Tvrtko Ursulin (2017-06-21 14:33:59)
>
> On 21/06/2017 13:48, Chris Wilson wrote:
> > Highly unlikely, but if the stop_machine() did suspend the tasklet, we
> > want to make sure that when it wakes it finds there is nothing to do.
> > Otherwise, it will loudly complain that the ELSP port tracking no longer
> > matches the hardware, and we will be mightly confused.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_gem.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 1353491c1010..ae3ce1314bd1 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3092,6 +3092,13 @@ static void engine_set_wedged(struct intel_engine_cs *engine)
> > engine->execlist_first = NULL;
> >
> > spin_unlock_irqrestore(&engine->timeline->lock, flags);
> > +
> > + /* The port is checked prior to scheduling a tasklet, but
> > + * just in case we have suspended the tasklet to do the
> > + * wedging make sure that when it wakes, it decides there
> > + * is no work to do by clearing the irq_posted bit.
> > + */
> > + clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
> > }
> > }
> >
> >
>
> Or tasklet_kill?
Hmm, technically not permitted:
void tasklet_kill(struct tasklet_struct *t)
{
if (in_interrupt())
pr_notice("Attempt to kill tasklet from interrupt\n");
while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
do {
yield();
} while (test_bit(TASKLET_STATE_SCHED, &t->state));
}
tasklet_unlock_wait(t);
clear_bit(TASKLET_STATE_SCHED, &t->state);
}
Even if we don't trigger the in_interrupt() simply due to having
interrupts disabled, then the potential yield() is illegal from inside
stop_machine().
-Chris
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