On one of the sharded runs igt@gem_wait@basic-busy-write-all failed giving following error: 

Out	
IGT-Version: 1.19-gbf45d253 (x86_64) (Linux: 4.13.0-rc7-CI-CI_DRM_3016+ x86_64)
Stack trace:
  #0 [__igt_fail_assert+0x101]
  #1 [basic+0x30e]
  #2 [__real_main163+0x541]
  #3 [main+0x33]
  #4 [__libc_start_main+0xf1]
  #5 [_start+0x2a]
  #6 [<unknown>+0x2a]
Subtest basic-busy-write-all: FAIL (1.099s)
Err	
(gem_wait:1964) CRITICAL: Test assertion failure function basic, file gem_wait.c:134:
(gem_wait:1964) CRITICAL: Failed assertion: igt_seconds_elapsed(&tv) < timeout
Subtest basic-busy-write-all failed.
**** DEBUG ****
(gem_wait:1964) igt-debugfs-DEBUG: Opening debugfs directory '/sys/kernel/debug/dri/0'
(gem_wait:1964) drmtest-DEBUG: Test requirement passed: !(fd<0)
(gem_wait:1964) drmtest-DEBUG: Test requirement passed: is_i915_device(fd) && has_known_intel_chipset(fd)
(gem_wait:1964) ioctl-wrappers-DEBUG: Test requirement passed: err == 0
(gem_wait:1964) igt-dummyload-DEBUG: Test requirement passed: nengine
(gem_wait:1964) CRITICAL: Test assertion failure function basic, file gem_wait.c:134:
(gem_wait:1964) CRITICAL: Failed assertion: igt_seconds_elapsed(&tv) < timeout
(gem_wait:1964) igt-core-INFO: Stack trace:
(gem_wait:1964) igt-core-INFO:   #0 [__igt_fail_assert+0x101]
(gem_wait:1964) igt-core-INFO:   #1 [basic+0x30e]
(gem_wait:1964) igt-core-INFO:   #2 [__real_main163+0x541]
(gem_wait:1964) igt-core-INFO:   #3 [main+0x33]
(gem_wait:1964) igt-core-INFO:   #4 [__libc_start_main+0xf1]
(gem_wait:1964) igt-core-INFO:   #5 [_start+0x2a]
(gem_wait:1964) igt-core-INFO:   #6 [<unknown>+0x2a]
****  END  ****
Environment	
PIGLIT_PLATFORM="mixed_glx_egl" PIGLIT_SOURCE_DIR="/opt/igt/piglit"
Command	
/opt/igt/tests/gem_wait --run-subtest basic-busy-write-all

Link to error and logs:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3016/shard-snb5/igt@gem_wait@basic-busy-write-all.html

Dmesg(also on above link) 
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3016/shard-snb5/dmesg20.log