[Intel-gfx] [PATCH igt] lib/gt: Insert an arbitration point in our hang batch

[Chris Wilson]

A purely recursive batch has the downside that it is a severe drain on
system resources (see commit f978cc027cd0 "lib/dummyload: Pad with a few
nops so that we do not completely hog the system") which can result in
the test being starved and failing to make reasonably progress. For more
reliable resets, also include an arbitration point. This should lessen
the efficacy of the hang...

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 lib/igt_gt.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/igt_gt.c b/lib/igt_gt.c
index 89727d22..2aebad14 100644
--- a/lib/igt_gt.c
+++ b/lib/igt_gt.c
@@ -313,12 +313,12 @@ igt_hang_t igt_hang_ctx(int fd,
 	len = 2;
 	if (intel_gen(intel_get_drm_devid(fd)) >= 8)
 		len++;
-	b[0] = MI_BATCH_BUFFER_START | (len - 2);
-	b[len] = MI_BATCH_BUFFER_END;
-	b[len+1] = MI_NOOP;
-	gem_write(fd, exec.handle, 0, b, sizeof(b));
+	b[0] = 0x5 << 24; /* ARB_CHk */
+	b[1] = MI_BATCH_BUFFER_START | (len - 2);
+	b[len+1] = MI_BATCH_BUFFER_END;
+	gem_write(fd, exec.handle, 4096-sizeof(b), b, sizeof(b));
 
-	reloc.offset = sizeof(uint32_t);
+	reloc.offset = 4096 - sizeof(b) + 2*sizeof(uint32_t);
 	reloc.target_handle = exec.handle;
 	reloc.read_domains = I915_GEM_DOMAIN_COMMAND;
 
-- 
2.15.0.rc2