[PATCH 7/7] drm/i915: Remove waiting & retiring from shrinker paths

[Chris Wilson]

i915_gem_wait_for_idle() and i915_retire_requests() introduce a
dependency on the timeline->mutex. This is problematic as we want to
later perform allocations underneath i915_active.mutex, forming a link
between the shrinker, the timeline and active mutexes. Nip this cycle in
the bud by removing the acquisition of the timeline mutex (i.e.
retiring) from inside the shrinker.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_shrinker.c          | 10 ----------
 drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c |  3 +++
 drivers/gpu/drm/i915/i915_drv.h                       |  2 +-
 drivers/gpu/drm/i915/i915_timeline.c                  |  3 ---
 4 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
index 3a926a8755c6..1bbc690494c7 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
@@ -169,7 +169,6 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	 */
 
 	trace_i915_gem_shrink(i915, target, shrink);
-	i915_retire_requests(i915);
 
 	/*
 	 * Unbinding of objects will require HW access; Let us not wake the
@@ -269,8 +268,6 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	if (shrink & I915_SHRINK_BOUND)
 		intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 
-	i915_retire_requests(i915);
-
 	shrinker_unlock(i915, unlock);
 
 	if (nr_scanned)
@@ -427,12 +424,6 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 	if (!shrinker_lock(i915, 0, &unlock))
 		return NOTIFY_DONE;
 
-	/* Force everything onto the inactive lists */
-	if (i915_gem_wait_for_idle(i915,
-				   I915_WAIT_LOCKED,
-				   MAX_SCHEDULE_TIMEOUT))
-		goto out;
-
 	with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 		freed_pages += i915_gem_shrink(i915, -1UL, NULL,
 					       I915_SHRINK_BOUND |
@@ -455,7 +446,6 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 	}
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
-out:
 	shrinker_unlock(i915, unlock);
 
 	*(unsigned long *)ptr += freed_pages;
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
index f2d4e773404a..52ad4563cb85 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -428,6 +428,9 @@ create_test_object(struct i915_gem_context *ctx,
 	u64 size;
 	int err;
 
+	/* Keep in GEM's good graces */
+	i915_retire_requests(ctx->i915);
+
 	size = min(vm->total / 2, 1024ull * DW_PER_PAGE * PAGE_SIZE);
 	size = round_down(size, DW_PER_PAGE * PAGE_SIZE);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bc909ec5d9c3..c6e24503e80d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1826,7 +1826,7 @@ struct drm_i915_private {
 	/* Abstract the submission mechanism (legacy ringbuffer or execlists) away */
 	struct {
 		struct i915_gt_timelines {
-			struct mutex mutex; /* protects list, tainted by GPU */
+			struct mutex mutex; /* protects list */
 			struct list_head active_list;
 
 			/* Pack multiple timelines' seqnos into the same page */
diff --git a/drivers/gpu/drm/i915/i915_timeline.c b/drivers/gpu/drm/i915/i915_timeline.c
index c311ce9c6f9d..f3ee264d7dd5 100644
--- a/drivers/gpu/drm/i915/i915_timeline.c
+++ b/drivers/gpu/drm/i915/i915_timeline.c
@@ -270,9 +270,6 @@ void i915_timelines_init(struct drm_i915_private *i915)
 
 	spin_lock_init(&gt->hwsp_lock);
 	INIT_LIST_HEAD(&gt->hwsp_free_list);
-
-	/* via i915_gem_wait_for_idle() */
-	i915_gem_shrinker_taints_mutex(i915, &gt->mutex);
 }
 
 static void timeline_add_to_active(struct i915_timeline *tl)
-- 
2.20.1