In a simple test case that writes to scratch and then busy-waits for the
batch to be signaled, we observe that the signal is before the write is
posted. That is bad news.
Splitting the flush + write_dword into two separate flush_dw prevents
the issue from being reproduced, we can presume the post-sync op is not
so post-sync.
Testcase: igt/gem_exec_fence/parallel
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/i915/gt/intel_lrc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index d0be98b67138..a437140a987d 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -5047,7 +5047,8 @@ gen12_emit_fini_breadcrumb_tail(struct i915_request *request, u32 *cs)
static u32 *gen12_emit_fini_breadcrumb(struct i915_request *rq, u32 *cs)
{
- return gen12_emit_fini_breadcrumb_tail(rq, emit_xcs_breadcrumb(rq, cs));
+ cs = emit_xcs_breadcrumb(rq, __gen8_emit_flush_dw(cs, 0, 0, 0));
+ return gen12_emit_fini_breadcrumb_tail(rq, cs);
}
static u32 *
--
2.20.1
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