[PATCH 2/3] drm/i915: fix invalid reference handling of the default ctx obj

Chris Wilson
2012-07-15T11:35:16Z

Otherwise we end up trying to unpin a freed object and BUG.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
---
drivers/gpu/drm/i915/i915_gem_context.c | 18 ++++--------------
1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index fd978bb..0cfc9d2 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -415,8 +415,11 @@ static int do_switch(struct drm_i915_gem_object *from_obj,
from_obj->dirty = 1;
BUG_ON(from_obj->ring != to->ring);
i915_gem_object_unpin(from_obj);
+
+ drm_gem_object_unreference(&from_obj->base);
}

+ drm_gem_object_reference(&to->obj->base);
ring->last_context_obj = to->obj;
to->is_initialized = true;

@@ -466,20 +469,7 @@ int i915_switch_context(struct intel_ring_buffer *ring,
if (from_obj == to->obj)
return 0;

- ret = do_switch(from_obj, to, i915_gem_next_request_seqno(to->ring));
- if (ret)
- return ret;
-
- /* Just to make the code a little cleaner we take the object reference
- * after the switch was successful. It would be more intuitive to ref
- * the 'to' object before the switch but we know the refcount must be >0
- * if context_get() succeeded, and we hold struct mutex. So it's safe to
- * do this here/now
- */
- drm_gem_object_reference(&to->obj->base);
- if (from_obj != NULL)
- drm_gem_object_unreference(&from_obj->base);
- return ret;
+ return do_switch(from_obj, to, i915_gem_next_request_seqno(to->ring));
}

int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
--
1.7.10.4