From 922d369b2922b3bb8c72aadddbd7445e6dc1183a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 15 Sep 2020 10:14:17 +0100 Subject: drm/i915/gt: Clear the buffer pool age before use If we create a new node, it is possible for the slab allocator to return us a recently freed node. If that node was just retired, it will retain the current jiffy as its node->age. There is then a miniscule window, where as that node is retired, it will appear on the free list with an incorrect age and be eligible for reuse by one thread, and then by a second thread as the correct node->age is written. Fixes: 06b73c2d0b65 ("drm/i915/gt: Delay taking the spinlock for grabbing from the buffer pool") Signed-off-by: Chris Wilson Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20200915091417.4086-3-chris@chris-wilson.co.uk (cherry picked from commit 9bb34ff25c458a2a48fb61409df42f465ede37f8) Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/gpu/drm/i915') 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 4b7671ac5dca..104cb30e8c13 100644 --- a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c +++ b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c @@ -134,6 +134,7 @@ static void pool_retire(struct i915_active *ref) /* Return this object to the shrinker pool */ i915_gem_object_make_purgeable(node->obj); + GEM_BUG_ON(node->age); spin_lock_irqsave(&pool->lock, flags); list_add_rcu(&node->link, list); WRITE_ONCE(node->age, jiffies ?: 1); /* 0 reserved for active nodes */ @@ -155,6 +156,7 @@ node_create(struct intel_gt_buffer_pool *pool, size_t sz) if (!node) return ERR_PTR(-ENOMEM); + node->age = 0; node->pool = pool; i915_active_init(&node->active, pool_active, pool_retire); -- cgit