From: Chris Wilson Date: Fri, 11 Jul 2014 10:28:01 +0000 (+0100) Subject: drm/i915: Initialise userptr mmu_notifier serial to 1 X-Git-Tag: firefly_0821_release~176^2~3450^2~20^2~32 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6c308fecb4d1f928d52f9586d976f79b37149388;p=firefly-linux-kernel-4.4.55.git drm/i915: Initialise userptr mmu_notifier serial to 1 During the range invalidate, we walk the list of buffers associated with the mmu_notifer and find the ones that overlap the range. An optimisation is made to speed up the iteration by assuming the previous iter is still valid whilst the tree is unmodified. This exposes a bug when a range invalidate is triggered after we have just created the mmu_notifier, but before attaching any buffers. In that case, we presume we have an unmodified list and start walking from the last iter which is NULL. Oops. The easiest fix is then to initialise the serial of the tree to 1. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin Testecase: igt/gem_userptr_blts/stress-mm Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 21ea92886a56..b41614df8927 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -150,7 +150,7 @@ i915_mmu_notifier_get(struct drm_device *dev, struct mm_struct *mm) mmu->mm = mm; mmu->objects = RB_ROOT; mmu->count = 0; - mmu->serial = 0; + mmu->serial = 1; /* Protected by mmap_sem (write-lock) */ ret = __mmu_notifier_register(&mmu->mn, mm);