[PATCH 5.19 056/207] drm/i915/gem: Flush contexts on driver release

Greg Kroah-Hartman
2022-09-26T11:41:17Z

From: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>

commit 5ce8f7444f8fbb5adee644590c0e4e1890ab004c upstream.

Due to i915_perf assuming that it can use the i915_gem_context reference
to protect its i915->gem.contexts.list iteration, we need to defer removal
of the context from the list until last reference to the context is put.
However, there is a risk of triggering kernel warning on contexts list not
empty at driver release time if we deleagate that task to a worker for
i915_gem_context_release_work(), unless that work is flushed first.
Unfortunately, it is not flushed on driver release. Fix it.

Instead of additionally calling flush_workqueue(), either directly or via
a new dedicated wrapper around it, replace last call to
i915_gem_drain_freed_objects() with existing i915_gem_drain_workqueue()
that performs both tasks.

Fixes: 75eefd82581f ("drm/i915: Release i915_gem_context from a worker")
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: stable@kernel.org # v5.16+
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916092403.201355-2-janusz.krzysztofik@linux.intel.com
(cherry picked from commit 1cec34442408a77ba5396b19725fed2c398005c3)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/i915/i915_gem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1191,7 +1191,8 @@ void i915_gem_driver_release(struct drm_

intel_uc_cleanup_firmwares(&to_gt(dev_priv)->uc);

- i915_gem_drain_freed_objects(dev_priv);
+ /* Flush any outstanding work, including i915_gem_context.release_work. */
+ i915_gem_drain_workqueue(dev_priv);

drm_WARN_ON(&dev_priv->drm, !list_empty(&dev_priv->gem.contexts.list));
}