[Intel-gfx] [PATCH] drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree
Chris Wilson
chris at chris-wilson.co.uk
Wed Nov 13 18:53:59 UTC 2019
As we want to be able to run inside atomic context for retiring the
i915_active, and we are no longer allowed to abuse mutex_trylock, split
the tree management portion of i915_active.mutex into an irq-safe
spinlock.
References: a0855d24fc22d ("locking/mutex: Complain upon mutex API misuse in IRQ contexts")
References: https://bugs.freedesktop.org/show_bug.cgi?id=111626
Fixes: 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: Matthew Auld <matthew.auld at intel.com>
---
drivers/gpu/drm/i915/i915_active.c | 57 ++++++++++----------
drivers/gpu/drm/i915/i915_active_types.h | 1 +
drivers/gpu/drm/i915/selftests/i915_active.c | 4 +-
3 files changed, 31 insertions(+), 31 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 207383dda84d..5448f37c8102 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -91,14 +91,15 @@ static void debug_active_init(struct i915_active *ref)
static void debug_active_activate(struct i915_active *ref)
{
- lockdep_assert_held(&ref->mutex);
+ spin_lock_irq(&ref->tree_lock);
if (!atomic_read(&ref->count)) /* before the first inc */
debug_object_activate(ref, &active_debug_desc);
+ spin_unlock_irq(&ref->tree_lock);
}
static void debug_active_deactivate(struct i915_active *ref)
{
- lockdep_assert_held(&ref->mutex);
+ lockdep_assert_held(&ref->tree_lock);
if (!atomic_read(&ref->count)) /* after the last dec */
debug_object_deactivate(ref, &active_debug_desc);
}
@@ -128,29 +129,22 @@ __active_retire(struct i915_active *ref)
{
struct active_node *it, *n;
struct rb_root root;
- bool retire = false;
+ unsigned long flags;
- lockdep_assert_held(&ref->mutex);
GEM_BUG_ON(i915_active_is_idle(ref));
/* return the unused nodes to our slabcache -- flushing the allocator */
- if (atomic_dec_and_test(&ref->count)) {
- debug_active_deactivate(ref);
- root = ref->tree;
- ref->tree = RB_ROOT;
- ref->cache = NULL;
- retire = true;
- }
-
- mutex_unlock(&ref->mutex);
- if (!retire)
+ if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))
return;
GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));
- rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
- GEM_BUG_ON(i915_active_fence_isset(&it->base));
- kmem_cache_free(global.slab_cache, it);
- }
+ debug_active_deactivate(ref);
+
+ root = ref->tree;
+ ref->tree = RB_ROOT;
+ ref->cache = NULL;
+
+ spin_unlock_irqrestore(&ref->tree_lock, flags);
/* After the final retire, the entire struct may be freed */
if (ref->retire)
@@ -158,6 +152,11 @@ __active_retire(struct i915_active *ref)
/* ... except if you wait on it, you must manage your own references! */
wake_up_var(ref);
+
+ rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
+ GEM_BUG_ON(i915_active_fence_isset(&it->base));
+ kmem_cache_free(global.slab_cache, it);
+ }
}
static void
@@ -169,7 +168,6 @@ active_work(struct work_struct *wrk)
if (atomic_add_unless(&ref->count, -1, 1))
return;
- mutex_lock(&ref->mutex);
__active_retire(ref);
}
@@ -180,9 +178,7 @@ active_retire(struct i915_active *ref)
if (atomic_add_unless(&ref->count, -1, 1))
return;
- /* If we are inside interrupt context (fence signaling), defer */
- if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS ||
- !mutex_trylock(&ref->mutex)) {
+ if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
queue_work(system_unbound_wq, &ref->work);
return;
}
@@ -227,7 +223,7 @@ active_instance(struct i915_active *ref, struct intel_timeline *tl)
if (!prealloc)
return NULL;
- mutex_lock(&ref->mutex);
+ spin_lock_irq(&ref->tree_lock);
GEM_BUG_ON(i915_active_is_idle(ref));
parent = NULL;
@@ -257,7 +253,7 @@ active_instance(struct i915_active *ref, struct intel_timeline *tl)
out:
ref->cache = node;
- mutex_unlock(&ref->mutex);
+ spin_unlock_irq(&ref->tree_lock);
BUILD_BUG_ON(offsetof(typeof(*node), base));
return &node->base;
@@ -278,8 +274,10 @@ void __i915_active_init(struct i915_active *ref,
if (bits & I915_ACTIVE_MAY_SLEEP)
ref->flags |= I915_ACTIVE_RETIRE_SLEEPS;
+ spin_lock_init(&ref->tree_lock);
ref->tree = RB_ROOT;
ref->cache = NULL;
+
init_llist_head(&ref->preallocated_barriers);
atomic_set(&ref->count, 0);
__mutex_init(&ref->mutex, "i915_active", key);
@@ -510,7 +508,7 @@ static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
if (RB_EMPTY_ROOT(&ref->tree))
return NULL;
- mutex_lock(&ref->mutex);
+ spin_lock_irq(&ref->tree_lock);
GEM_BUG_ON(i915_active_is_idle(ref));
/*
@@ -575,7 +573,7 @@ static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
goto match;
}
- mutex_unlock(&ref->mutex);
+ spin_unlock_irq(&ref->tree_lock);
return NULL;
@@ -583,7 +581,7 @@ static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
if (p == &ref->cache->node)
ref->cache = NULL;
- mutex_unlock(&ref->mutex);
+ spin_unlock_irq(&ref->tree_lock);
return rb_entry(p, struct active_node, node);
}
@@ -664,6 +662,7 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
void i915_active_acquire_barrier(struct i915_active *ref)
{
struct llist_node *pos, *next;
+ unsigned long flags;
GEM_BUG_ON(i915_active_is_idle(ref));
@@ -673,7 +672,7 @@ void i915_active_acquire_barrier(struct i915_active *ref)
* populated by i915_request_add_active_barriers() to point to the
* request that will eventually release them.
*/
- mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING);
+ spin_lock_irqsave_nested(&ref->tree_lock, flags, SINGLE_DEPTH_NESTING);
llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
struct active_node *node = barrier_from_ll(pos);
struct intel_engine_cs *engine = barrier_to_engine(node);
@@ -699,7 +698,7 @@ void i915_active_acquire_barrier(struct i915_active *ref)
llist_add(barrier_to_ll(node), &engine->barrier_tasks);
intel_engine_pm_put(engine);
}
- mutex_unlock(&ref->mutex);
+ spin_unlock_irqrestore(&ref->tree_lock, flags);
}
void i915_request_add_active_barriers(struct i915_request *rq)
diff --git a/drivers/gpu/drm/i915/i915_active_types.h b/drivers/gpu/drm/i915/i915_active_types.h
index d89a74c142c6..96aed0ee700a 100644
--- a/drivers/gpu/drm/i915/i915_active_types.h
+++ b/drivers/gpu/drm/i915/i915_active_types.h
@@ -48,6 +48,7 @@ struct i915_active {
atomic_t count;
struct mutex mutex;
+ spinlock_t tree_lock;
struct active_node *cache;
struct rb_root tree;
diff --git a/drivers/gpu/drm/i915/selftests/i915_active.c b/drivers/gpu/drm/i915/selftests/i915_active.c
index f3fa05c78d78..60290f78750d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_active.c
+++ b/drivers/gpu/drm/i915/selftests/i915_active.c
@@ -277,8 +277,8 @@ void i915_active_unlock_wait(struct i915_active *ref)
}
/* And wait for the retire callback */
- mutex_lock(&ref->mutex);
- mutex_unlock(&ref->mutex);
+ spin_lock_irq(&ref->tree_lock);
+ spin_unlock_irq(&ref->tree_lock);
/* ... which may have been on a thread instead */
flush_work(&ref->work);
--
2.24.0
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