dev_priv keeps track of the current addressing mode that gets set at
execbuffer time. Unfortunately the existing code was doing this before
acquiring struct_mutex which leaves a race with another thread also
doing an execbuffer. If that wasn't bad enough, relocate_slow drops
struct_mutex which opens a much more likely error where another thread
comes in and modifies the state while relocate_slow is being slow.
The solution here is to just defer setting this state until we
absolutely need it, and we know we'll have struct_mutex for the
remainder of our code path.
v2: Keith noticed a bug in the original patch.
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 29 +++++++++++++++------------
1 files changed, 16 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 3693e83..be0e3bc 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1016,19 +1016,6 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
if (INTEL_INFO(dev)->gen > 5 &&
mode == I915_EXEC_CONSTANTS_REL_SURFACE)
return -EINVAL;
-
- ret = intel_ring_begin(ring, 4);
- if (ret)
- return ret;
-
- intel_ring_emit(ring, MI_NOOP);
- intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
- intel_ring_emit(ring, INSTPM);
- intel_ring_emit(ring,
- I915_EXEC_CONSTANTS_MASK << 16 | mode);
- intel_ring_advance(ring);
-
- dev_priv->relative_constants_mode = mode;
}
break;
default:
@@ -1159,6 +1146,22 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
}
}
+ if (ring == &dev_priv->ring[RCS] &&
+ mode != dev_priv->relative_constants_mode) {
+ ret = intel_ring_begin(ring, 4);
+ if (ret)
+ goto err;
+
+ intel_ring_emit(ring, MI_NOOP);
+ intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
+ intel_ring_emit(ring, INSTPM);
+ intel_ring_emit(ring,
+ I915_EXEC_CONSTANTS_MASK << 16 | mode);
+ intel_ring_advance(ring);
+
+ dev_priv->relative_constants_mode = mode;
+ }
+
trace_i915_gem_ring_dispatch(ring, seqno);
exec_start = batch_obj->gtt_offset + args->batch_start_offset;
--
1.7.8
