[Intel-gfx] [CI 2/4] drm/i915/gt: Convert timeline tracking to spinlock

[Chris Wilson]

Convert the active_list manipulation of timelines to use spinlocks so
that we can perform the updates from underneath a quick interrupt
callback, if need be.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Matthew Auld <matthew.a...@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_gt_types.h |  2 +-
 drivers/gpu/drm/i915/gt/intel_reset.c    | 10 ++++++++--
 drivers/gpu/drm/i915/gt/intel_timeline.c | 12 +++++-------
 drivers/gpu/drm/i915/i915_gem.c          | 14 +++++++-------
 4 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h 
b/drivers/gpu/drm/i915/gt/intel_gt_types.h
index adab4d2c29ac..143b2d78c2cc 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
@@ -40,7 +40,7 @@ struct intel_gt {
        struct intel_uc uc;
 
        struct intel_gt_timelines {
-               struct mutex mutex; /* protects list */
+               spinlock_t lock; /* protects active_list */
                struct list_head active_list;
 
                /* Pack multiple timelines' seqnos into the same page */
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c 
b/drivers/gpu/drm/i915/gt/intel_reset.c
index ec85740de942..077716442c90 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -811,7 +811,7 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
         *
         * No more can be submitted until we reset the wedged bit.
         */
-       mutex_lock(&timelines->mutex);
+       spin_lock(&timelines->lock);
        list_for_each_entry(tl, &timelines->active_list, link) {
                struct i915_request *rq;
 
@@ -819,6 +819,8 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
                if (!rq)
                        continue;
 
+               spin_unlock(&timelines->lock);
+
                /*
                 * All internal dependencies (i915_requests) will have
                 * been flushed by the set-wedge, but we may be stuck waiting
@@ -828,8 +830,12 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
                 */
                dma_fence_default_wait(&rq->fence, false, MAX_SCHEDULE_TIMEOUT);
                i915_request_put(rq);
+
+               /* Restart iteration after droping lock */
+               spin_lock(&timelines->lock);
+               tl = list_entry(&timelines->active_list, typeof(*tl), link);
        }
-       mutex_unlock(&timelines->mutex);
+       spin_unlock(&timelines->lock);
 
        intel_gt_sanitize(gt, false);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c 
b/drivers/gpu/drm/i915/gt/intel_timeline.c
index 4af0b9801d91..355dfc52c804 100644
--- a/drivers/gpu/drm/i915/gt/intel_timeline.c
+++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
@@ -266,7 +266,7 @@ static void timelines_init(struct intel_gt *gt)
 {
        struct intel_gt_timelines *timelines = &gt->timelines;
 
-       mutex_init(&timelines->mutex);
+       spin_lock_init(&timelines->lock);
        INIT_LIST_HEAD(&timelines->active_list);
 
        spin_lock_init(&timelines->hwsp_lock);
@@ -345,9 +345,9 @@ void intel_timeline_enter(struct intel_timeline *tl)
                return;
        GEM_BUG_ON(!tl->active_count); /* overflow? */
 
-       mutex_lock(&timelines->mutex);
+       spin_lock(&timelines->lock);
        list_add(&tl->link, &timelines->active_list);
-       mutex_unlock(&timelines->mutex);
+       spin_unlock(&timelines->lock);
 }
 
 void intel_timeline_exit(struct intel_timeline *tl)
@@ -358,9 +358,9 @@ void intel_timeline_exit(struct intel_timeline *tl)
        if (--tl->active_count)
                return;
 
-       mutex_lock(&timelines->mutex);
+       spin_lock(&timelines->lock);
        list_del(&tl->link);
-       mutex_unlock(&timelines->mutex);
+       spin_unlock(&timelines->lock);
 
        /*
         * Since this timeline is idle, all bariers upon which we were waiting
@@ -548,8 +548,6 @@ static void timelines_fini(struct intel_gt *gt)
 
        GEM_BUG_ON(!list_empty(&timelines->active_list));
        GEM_BUG_ON(!list_empty(&timelines->hwsp_free_list));
-
-       mutex_destroy(&timelines->mutex);
 }
 
 void intel_timelines_fini(struct drm_i915_private *i915)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b4c39a06fee5..07da7d5f855a 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -897,18 +897,18 @@ static long
 wait_for_timelines(struct drm_i915_private *i915,
                   unsigned int flags, long timeout)
 {
-       struct intel_gt_timelines *gt = &i915->gt.timelines;
+       struct intel_gt_timelines *timelines = &i915->gt.timelines;
        struct intel_timeline *tl;
 
-       mutex_lock(&gt->mutex);
-       list_for_each_entry(tl, &gt->active_list, link) {
+       spin_lock(&timelines->lock);
+       list_for_each_entry(tl, &timelines->active_list, link) {
                struct i915_request *rq;
 
                rq = i915_active_request_get_unlocked(&tl->last_request);
                if (!rq)
                        continue;
 
-               mutex_unlock(&gt->mutex);
+               spin_unlock(&timelines->lock);
 
                /*
                 * "Race-to-idle".
@@ -928,10 +928,10 @@ wait_for_timelines(struct drm_i915_private *i915,
                        return timeout;
 
                /* restart after reacquiring the lock */
-               mutex_lock(&gt->mutex);
-               tl = list_entry(&gt->active_list, typeof(*tl), link);
+               spin_lock(&timelines->lock);
+               tl = list_entry(&timelines->active_list, typeof(*tl), link);
        }
-       mutex_unlock(&gt->mutex);
+       spin_unlock(&timelines->lock);
 
        return timeout;
 }
-- 
2.23.0.rc1

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