Quoting Tvrtko Ursulin (2017-12-13 10:54:55)
>
> On 13/12/2017 09:48, Chris Wilson wrote:
> > It is illegal to perform an immediate free of the struct irq_work from
> > inside the irq_work callback (as irq_work_run_list modifies work->flags
> > after execution of the work->func()). As we use the irq_work to
> > coordinate the freeing of the callback from two different softirq paths,
> > we need to defer the kfree from inside our irq_work callback, for which
> > we can use kfree_rcu.
> >
> > Fixes: 81c0ed21aa91 ("drm/i915/fence: Avoid del_timer_sync() from inside a timer")
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_sw_fence.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
> > index e8ca67a129d2..ac236b88c99c 100644
> > --- a/drivers/gpu/drm/i915/i915_sw_fence.c
> > +++ b/drivers/gpu/drm/i915/i915_sw_fence.c
> > @@ -367,6 +367,7 @@ struct i915_sw_dma_fence_cb {
> > struct dma_fence *dma;
> > struct timer_list timer;
> > struct irq_work work;
> > + struct rcu_head rcu;
> > };
> >
> > static void timer_i915_sw_fence_wake(struct timer_list *t)
> > @@ -406,7 +407,7 @@ static void irq_i915_sw_fence_work(struct irq_work *wrk)
> > del_timer_sync(&cb->timer);
> > dma_fence_put(cb->dma);
> >
> > - kfree(cb);
> > + kfree_rcu(cb, rcu);
> > }
> >
> > int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
> >
>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Ta, applied. Still hopeful this was more than a one-off on my poor
Braswell.
-Chris
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