Re: [PATCH v4] drm/i915: get a runtime PM ref for the deferred GPU reset work

Daniel Vetter
2014-04-23T07:07:36Z

On Wed, Apr 23, 2014 at 01:13:40AM +0300, Imre Deak wrote:
> Atm we can end up in the GPU reset deferred work in D3 state if the last
> runtime PM reference is dropped between detecting a hang/scheduling the
> work and executing the work. At least one such case I could trigger is
> the simulated reset via the i915_wedged debugfs entry. Fix this by
> getting an RPM reference around accessing the HW in the reset work.
>
> v2:
> - Instead of getting/putting the RPM reference in the reset work itself,
> get it already before scheduling the work. By this we also prevent
> going to D3 before the work gets to run, in addition to making sure
> that we run the work itself in D0. (Ville, Daniel)
> v3:
> - fix inverted logic fail when putting the RPM ref on behalf of a
> cancelled GPU reset work (Ville)
> v4:
> - Taking the RPM ref in the interrupt handler isn't really needed b/c
> it's already guaranteed that we hold an RPM ref until the end of the
> reset work in all cases we care about. So take the ref in the reset
> work (for cases like i915_wedged_set). (Daniel)
>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
> drivers/gpu/drm/i915/i915_irq.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index a651d0d..0e47111 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -2175,6 +2175,14 @@ static void i915_error_work_func(struct work_struct *work)
> reset_event);
>
> /*
> + * In most cases it's guaranteed that we get here with an RPM
> + * reference held, for example because there is a pending GPU
> + * request that won't finish until the reset is done. This
> + * isn't the case at least when we get here by doing a
> + * simulated reset via debugs, so get an RPM reference.

^debugfs

Also maybe "..., so get a RPM reference just to quiet the warnings."
-Daniel

> + */
> + intel_runtime_pm_get(dev_priv);
> + /*
> * All state reset _must_ be completed before we update the
> * reset counter, for otherwise waiters might miss the reset
> * pending state and not properly drop locks, resulting in
> @@ -2184,6 +2192,8 @@ static void i915_error_work_func(struct work_struct *work)
>
> intel_display_handle_reset(dev);
>
> + intel_runtime_pm_put(dev_priv);
> +
> if (ret == 0) {
> /*
> * After all the gem state is reset, increment the reset
> --
> 1.8.4
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch