[Intel-gfx] [PATCH] drm/i915/gem: Keep request alive while attaching fences

[Chris Wilson]

Since commit e5dadff4b093 ("drm/i915: Protect request retirement with
timeline->mutex"), the request retirement can happen outside of the
struct_mutex serialised only by the timeline->mutex. We drop the
timeline->mutex on submitting the request (i915_request_add) so after
that point, it is liable to be freed. Make sure our local reference is
kept alive until we have finished attaching it to the signalers. (Note
that this erodes the argument that i915_request_add should consume the
reference, but that is a slightly larger patch!)

Fixes: e5dadff4b093 ("drm/i915: Protect request retirement with timeline->mutex")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 81eaf812c9da..7d07131aa3f7 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2730,6 +2730,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	err = eb_submit(&eb);
 err_request:
 	add_to_client(eb.request, file);
+	i915_request_get(eb.request);
 	i915_request_add(eb.request);
 
 	if (fences)
@@ -2745,6 +2746,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 			fput(out_fence->file);
 		}
 	}
+	i915_request_put(eb.request);
 
 err_batch_unpin:
 	if (eb.batch_flags & I915_DISPATCH_SECURE)
-- 
2.24.1