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drm/i915/gt: Pull release of node->age under the spinlock

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We need to ensure that the list is valid prior to marking the node as
retrievable, otherwise we may see two threads compete over the same node
in intel_gt_get_buffer_pool(). If the first thread acquires and releases
the node in the same jiffie, the second thread may then acquire it (as
the jiffie now again matches the expected value) and claim the node
before it is put back into the list.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730134049.8822-1-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
This commit is contained in:
Chris Wilson 2020-07-30 14:40:49 +01:00 committed by Joonas Lahtinen
parent d1bf5dd8f6
commit 13106019f7
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
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@ -134,9 +134,9 @@ static void pool_retire(struct i915_active *ref)
/* Return this object to the shrinker pool */
i915_gem_object_make_purgeable(node->obj);
WRITE_ONCE(node->age, jiffies ?: 1); /* 0 reserved for active nodes */
spin_lock_irqsave(&pool->lock, flags);
list_add_rcu(&node->link, list);
WRITE_ONCE(node->age, jiffies ?: 1); /* 0 reserved for active nodes */
spin_unlock_irqrestore(&pool->lock, flags);
schedule_delayed_work(&pool->work,