Quoting Tvrtko Ursulin (2019-01-03 12:23:29)
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> In a patch named "drm/i915: Return immediately if trylock fails for
> direct-reclaim" Chris Wilson implicitly suggests it is safe to use a plain
> mutex_lock instead of trylock on the I915_SHRINK_ACTIVE code paths.
>
> Explore this to see how the lockdep traces will look.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_shrinker.c | 11 ++---------
> 1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index 97deec775f40..2d4a54851c0a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -47,15 +47,8 @@ shrinker_lock(struct drm_i915_private *i915, unsigned int flags, bool *unlock)
> case MUTEX_TRYLOCK_FAILED:
> *unlock = false;
> if (flags & I915_SHRINK_ACTIVE) {
> - preempt_disable();
> - do {
> - cpu_relax();
> - if (mutex_trylock(&i915->drm.struct_mutex)) {
> - *unlock = true;
> - break;
> - }
> - } while (!need_resched());
> - preempt_enable();
> + mutex_lock(&i915->drm.struct_mutex);
You seemed to have lost some annotation here.
-Chris
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