From 304d695c3dc8eb65206b9eaf16f8d1a41510d1cf Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 2 Jan 2014 14:32:35 +0000 Subject: [PATCH] drm/i915: Flush outstanding requests before allocating new seqno In very rare cases (such as a memory failure stress test) it is possible to fill the entire ring without emitting a request. Under this circumstance, the outstanding request is flushed and waited upon. After space on the ring is cleared, we return to emitting the new command - except that we just cleared the seqno allocated for this operation and trigger the sanity check that a request is only ever emitted with a valid seqno. The fix is to rearrange the code to make sure the allocation of the seqno for this operation is after any required flushes of outstanding operations. The bug exists since the preallocation was introduced in commit 9d7730914f4cd496e356acfab95b41075aa8eae8 Author: Chris Wilson Date: Tue Nov 27 16:22:52 2012 +0000 drm/i915: Preallocate next seqno before touching the ring Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Daniel Vetter Cc: stable@vger.kernel.org Signed-off-by: Chris Wilson Reviewed-by: Jani Nikula Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_ringbuffer.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index b106984c722a..8fcb32a02cb4 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -1607,8 +1607,8 @@ intel_ring_alloc_seqno(struct intel_ring_buffer *ring) return i915_gem_get_seqno(ring->dev, &ring->outstanding_lazy_seqno); } -static int __intel_ring_begin(struct intel_ring_buffer *ring, - int bytes) +static int __intel_ring_prepare(struct intel_ring_buffer *ring, + int bytes) { int ret; @@ -1624,7 +1624,6 @@ static int __intel_ring_begin(struct intel_ring_buffer *ring, return ret; } - ring->space -= bytes; return 0; } @@ -1639,12 +1638,17 @@ int intel_ring_begin(struct intel_ring_buffer *ring, if (ret) return ret; + ret = __intel_ring_prepare(ring, num_dwords * sizeof(uint32_t)); + if (ret) + return ret; + /* Preallocate the olr before touching the ring */ ret = intel_ring_alloc_seqno(ring); if (ret) return ret; - return __intel_ring_begin(ring, num_dwords * sizeof(uint32_t)); + ring->space -= num_dwords * sizeof(uint32_t); + return 0; } void intel_ring_init_seqno(struct intel_ring_buffer *ring, u32 seqno) -- 2.20.1