We always try to do an unlocked wait before resorting to having a
blocking wait under the mutex - so we very rarely have to sleep under
the struct_mutex. However, when we do we want that wait to be as short
as possible as the struct_mutex is our BKL that will stall the driver and
all clients.
There should be no impact for all typical workloads.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c1c2765bb8d0..47d17b227a05 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -395,6 +395,15 @@ i915_gem_object_wait_fence(struct dma_fence *fence,
rps = NULL;
}
+ /* Very rarely do we wait whilst holding the mutex. We try to always
+ * do an unlocked wait before using a locked wait. However, when we
+ * have to resort to a locked wait, we want that wait to be as short
+ * as possible as the struct_mutex is our BKL that will stall the
+ * driver and all clients.
+ */
+ if (flags & I915_WAIT_LOCKED && rq->engine->schedule)
+ rq->engine->schedule(rq, I915_PRIORITY_MAX);
+
timeout = i915_wait_request(rq, flags, timeout);
out:
--
2.11.0
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