[Quantal][SRU][PATCH 1/1] drm/i915: EBUSY status handling added to i915_gem_fault().

[leann.ogasawara at canonical.com]

From: Dmitry Rogozhkin <dmitry.v.rogozhkin at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1087302

Subsequent threads returning EBUSY from vm_insert_pfn() was not handled
correctly. As a result concurrent access from new threads to
mmapped data caused SIGBUS.

Note that this fixes i-g-t/tests/gem_threaded_tiled_access.

Tested-by: Mika Kuoppala <mika.kuoppala at intel.com>
Signed-off-by: Dmitry Rogozhkin <dmitry.v.rogozhkin at intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
(cherry picked from commit e79e0fe380847493266fba557217e2773c61bd1b)

Signed-off-by: Leann Ogasawara <leann.ogasawara at canonical.com>
---
 drivers/gpu/drm/i915/i915_gem.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e4d0187..4406603 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1144,6 +1144,11 @@ out:
 	case 0:
 	case -ERESTARTSYS:
 	case -EINTR:
+	case -EBUSY:
+		/*
+		 * EBUSY is ok: this just means that another thread
+		 * already did the job.
+		 */
 		return VM_FAULT_NOPAGE;
 	case -ENOMEM:
 		return VM_FAULT_OOM;
-- 
1.7.9.5