| Message ID | 20200730134049.8822-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/gt: Pull release of node->age under the spinlock | expand |
On Thu, 30 Jul 2020 at 14:41, Chris Wilson <chris@chris-wilson.co.uk> wrote: > > 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>
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c index 9e938d4f6bfe..4b7671ac5dca 100644 --- a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c +++ b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c @@ -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,
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> --- drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)