[Intel-gfx] [PATCH] drm/i915: Fix preallocated barrier list append

[José Roberto de Souza]

Only the first and the last nodes were being added to
ref->preallocated_barriers.

I'm not familiar with this part of the code but if that is the
expected behavior it is leaking the nodes in between.

Renaming variables to make it more easy to read.

Fixes: 841350223816 ("drm/i915/gt: Drop mutex serialisation between context pin/unpin")
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/i915/i915_active.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 9d6830885d2e..3d2e7cf55e52 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -607,7 +607,7 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 					    struct intel_engine_cs *engine)
 {
 	intel_engine_mask_t tmp, mask = engine->mask;
-	struct llist_node *pos = NULL, *next;
+	struct llist_node *first = NULL, *last = NULL;
 	struct intel_gt *gt = engine->gt;
 	int err;
 
@@ -626,6 +626,7 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 	GEM_BUG_ON(!mask);
 	for_each_engine_masked(engine, gt, mask, tmp) {
 		u64 idx = engine->kernel_context->timeline->fence_context;
+		struct llist_node *prev = first;
 		struct active_node *node;
 
 		node = reuse_idle_barrier(ref, idx);
@@ -659,23 +660,23 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 		GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
 
 		GEM_BUG_ON(barrier_to_engine(node) != engine);
-		next = barrier_to_ll(node);
-		next->next = pos;
-		if (!pos)
-			pos = next;
+		first = barrier_to_ll(node);
+		first->next = prev;
+		if (!last)
+			last = first;
 		intel_engine_pm_get(engine);
 	}
 
 	GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
-	llist_add_batch(next, pos, &ref->preallocated_barriers);
+	llist_add_batch(first, last, &ref->preallocated_barriers);
 
 	return 0;
 
 unwind:
-	while (pos) {
-		struct active_node *node = barrier_from_ll(pos);
+	while (first) {
+		struct active_node *node = barrier_from_ll(first);
 
-		pos = pos->next;
+		first = first->next;
 
 		atomic_dec(&ref->count);
 		intel_engine_pm_put(barrier_to_engine(node));
-- 
2.25.0