[ 108/167] [PATCH] drm/i915: relative_constants_mode race fix
From: Ben Hutchings <hidden>
Date: 2012-05-09 06:10:14
Also in:
lkml
Subsystem:
drm drivers, intel drm i915 driver (meteor lake, dg2 and older excluding poulsbo, moorestown and derivative), the rest · Maintainers:
David Airlie, Simona Vetter, Jani Nikula, Joonas Lahtinen, Rodrigo Vivi, Tvrtko Ursulin, Linus Torvalds
3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ben Widawsky <redacted> commit e2971bdab2b761683353da383c0fd5ac704d1cca upstream. 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 <redacted> Reviewed-by: Daniel Vetter <redacted> Signed-off-by: Keith Packard <keithp@keithp.com> Signed-off-by: Ben Hutchings <redacted> --- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 29 +++++++++++++++------------- 1 file 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 c681dc1..68e5b41 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c@@ -1033,19 +1033,6 @@ 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:
@@ -1176,6 +1163,22 @@ 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;
--
1.7.10