Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> When setting up reset, we may need to recursively prepare an engine. In
> which case we should only synchronously flush the tasklets on the outer
> most call, the inner calls will then be inside an atomic section where
> the tasklet will never be run (and so the sync will never complete).
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 2 +-
> drivers/gpu/drm/i915/i915_gem.h | 7 +++++++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0dc369a9ec4d..aab1f5e77ae9 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3036,7 +3036,7 @@ i915_gem_reset_prepare_engine(struct intel_engine_cs *engine)
> * Turning off the execlists->tasklet until the reset is over
> * prevents the race.
> */
> - tasklet_disable(&engine->execlists.tasklet);
> + __tasklet_disable_once(&engine->execlists.tasklet);
It is debatable that could the naming be improved as
the 'once' is tied to the disable now.
__tasklet_disable_wait_[once|first].
I was going to insist on adding a comment tho,
but there it is already above, explaining
the recursion from set wedged.
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
>
> /*
> * We're using worker to queue preemption requests from the tasklet in
> diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
> index 525920404ede..af033e7c1c56 100644
> --- a/drivers/gpu/drm/i915/i915_gem.h
> +++ b/drivers/gpu/drm/i915/i915_gem.h
> @@ -26,6 +26,7 @@
> #define __I915_GEM_H__
>
> #include <linux/bug.h>
> +#include <linux/interrupt.h>
>
> struct drm_i915_private;
>
> @@ -72,4 +73,10 @@ struct drm_i915_private;
> void i915_gem_park(struct drm_i915_private *i915);
> void i915_gem_unpark(struct drm_i915_private *i915);
>
> +static inline void __tasklet_disable_once(struct tasklet_struct *t)
> +{
> + if (atomic_inc_return(&t->count) == 1)
> + tasklet_unlock_wait(t);
> +}
> +
> #endif /* __I915_GEM_H__ */
> --
> 2.17.0
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