[Intel-gfx] [PATCH 2/2] Revert "drm/i915/execlists: Use a local lock for dfs_link access"

[Tvrtko Ursulin]

On 28/11/2016 14:36, Chris Wilson wrote:
> This reverts commit 27745e829a5c ("drm/i915/execlists: Use a local lock
> for dfs_link access") as the struct_mutex was required to prevent
> concurrent retiring and freeing, now restored in the previous patch.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: David Weinehall <david.weinehall at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 0a09024d6ca3..b2c0d509e191 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -695,7 +695,6 @@ pt_lock_engine(struct i915_priotree *pt, struct intel_engine_cs *locked)
>
>  static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
>  {
> -	static DEFINE_MUTEX(lock);
>  	struct intel_engine_cs *engine = NULL;
>  	struct i915_dependency *dep, *p;
>  	struct i915_dependency stack;
> @@ -704,8 +703,8 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
>  	if (prio <= READ_ONCE(request->priotree.priority))
>  		return;
>
> -	/* Need global lock to use the temporary link inside i915_dependency */
> -	mutex_lock(&lock);
> +	/* Need BKL in order to use the temporary link inside i915_dependency */
> +	lockdep_assert_held(&request->i915->drm.struct_mutex);
>
>  	stack.signaler = &request->priotree;
>  	list_add(&stack.dfs_link, &dfs);
> @@ -772,8 +771,6 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
>  	if (engine)
>  		spin_unlock_irq(&engine->timeline->lock);
>
> -	mutex_unlock(&lock);
> -
>  	/* XXX Do we need to preempt to make room for us and our deps? */
>  }
>
>

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko