Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> We already use a mutex to serialise i915_reset() and wedging, so all we
> need it to link that into i915_request_wait() and we have our lock cycle
> detection.
>
> v2.5: Take error mutex for selftests
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_reset.c | 6 ++----
> drivers/gpu/drm/i915/i915_drv.h | 8 --------
> drivers/gpu/drm/i915/i915_gem.c | 3 ---
> drivers/gpu/drm/i915/i915_request.c | 12 ++++++++++--
> drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 --
> 5 files changed, 12 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> index 8ba7af8b7ced..41a294f5cc19 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -978,7 +978,7 @@ void i915_reset(struct drm_i915_private *i915,
>
> might_sleep();
> GEM_BUG_ON(!test_bit(I915_RESET_BACKOFF, &error->flags));
> - lock_map_acquire(&i915->gt.reset_lockmap);
> + mutex_lock(&error->wedge_mutex);
>
> /* Clear any previous failed attempts at recovery. Time to try again. */
> if (!__i915_gem_unset_wedged(i915))
> @@ -1031,7 +1031,7 @@ void i915_reset(struct drm_i915_private *i915,
> finish:
> reset_finish(i915);
> unlock:
> - lock_map_release(&i915->gt.reset_lockmap);
> + mutex_unlock(&error->wedge_mutex);
> return;
>
> taint:
> @@ -1147,9 +1147,7 @@ static void i915_reset_device(struct drm_i915_private *i915,
> /* Flush everyone using a resource about to be clobbered */
> synchronize_srcu_expedited(&error->reset_backoff_srcu);
>
> - mutex_lock(&error->wedge_mutex);
> i915_reset(i915, engine_mask, reason);
> - mutex_unlock(&error->wedge_mutex);
>
> intel_finish_reset(i915);
> }
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 90d94d904e65..3683ef6d4c28 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1901,14 +1901,6 @@ struct drm_i915_private {
> ktime_t last_init_time;
>
> struct i915_vma *scratch;
> -
> - /*
> - * We must never wait on the GPU while holding a lock as we
> - * may need to perform a GPU reset. So while we don't need to
> - * serialise wait/reset with an explicit lock, we do want
> - * lockdep to detect potential dependency cycles.
> - */
> - struct lockdep_map reset_lockmap;
> } gt;
>
> struct {
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 4bbded4aa936..7232361973fd 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1746,7 +1746,6 @@ static void i915_gem_init__mm(struct drm_i915_private *i915)
>
> int i915_gem_init_early(struct drm_i915_private *dev_priv)
> {
> - static struct lock_class_key reset_key;
> int err;
>
> intel_gt_pm_init(dev_priv);
> @@ -1754,8 +1753,6 @@ int i915_gem_init_early(struct drm_i915_private *dev_priv)
> INIT_LIST_HEAD(&dev_priv->gt.active_rings);
> INIT_LIST_HEAD(&dev_priv->gt.closed_vma);
> spin_lock_init(&dev_priv->gt.closed_lock);
> - lockdep_init_map(&dev_priv->gt.reset_lockmap,
> - "i915.reset", &reset_key, 0);
>
> i915_gem_init__mm(dev_priv);
> i915_gem_init__pm(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 1cbc3ef4fc27..5311286578b7 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -1444,7 +1444,15 @@ long i915_request_wait(struct i915_request *rq,
> return -ETIME;
>
> trace_i915_request_wait_begin(rq, flags);
> - lock_map_acquire(&rq->i915->gt.reset_lockmap);
> +
> + /*
> + * We must never wait on the GPU while holding a lock as we
> + * may need to perform a GPU reset. So while we don't need to
> + * serialise wait/reset with an explicit lock, we do want
> + * lockdep to detect potential dependency cycles.
> + */
> + mutex_acquire(&rq->i915->gpu_error.wedge_mutex.dep_map,
> + 0, 0, _THIS_IP_);
Seems to translate to exclusive lock with full checking.
There was ofcourse a slight possibilty that previous reviewer did
read all the lockdep.h. Looked at the wedge mutex and connected
the dots. Well, it is obvious now.
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
>
> /*
> * Optimistic spin before touching IRQs.
> @@ -1518,7 +1526,7 @@ long i915_request_wait(struct i915_request *rq,
> dma_fence_remove_callback(&rq->fence, &wait.cb);
>
> out:
> - lock_map_release(&rq->i915->gt.reset_lockmap);
> + mutex_release(&rq->i915->gpu_error.wedge_mutex.dep_map, 0, _THIS_IP_);
> trace_i915_request_wait_end(rq);
> return timeout;
> }
> diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> index 1e9ffced78c1..b7f3fbb4ae89 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> @@ -130,7 +130,6 @@ static struct dev_pm_domain pm_domain = {
>
> struct drm_i915_private *mock_gem_device(void)
> {
> - static struct lock_class_key reset_key;
> struct drm_i915_private *i915;
> struct pci_dev *pdev;
> int err;
> @@ -205,7 +204,6 @@ struct drm_i915_private *mock_gem_device(void)
> INIT_LIST_HEAD(&i915->gt.active_rings);
> INIT_LIST_HEAD(&i915->gt.closed_vma);
> spin_lock_init(&i915->gt.closed_lock);
> - lockdep_init_map(&i915->gt.reset_lockmap, "i915.reset", &reset_key, 0);
>
> mutex_lock(&i915->drm.struct_mutex);
>
> --
> 2.20.1
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