From: Chris Wilson <ch...@chris-wilson.co.uk> commit f6e98a1809faa02f40e0d089d6cfc1aa372a34c0 upstream.
The first thing the active retirement worker does is decrement the i915_active count. The first thing we do during i915_active_wait is try to increment the i915_active count, but only if already active [non-zero]. The wait may see that the retirement is already started and so marked the i915_active as idle, and skip waiting for the retirement handler. However, the caller of i915_active_wait may immediately free the i915_active upon returning (e.g. i915_vma_destroy) so we must not return before the concurrent access from the worker is completed. We must always flush the worker. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2473 Fixes: 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker") Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Matthew Auld <matthew.a...@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com> Cc: <sta...@vger.kernel.org> # v5.5+ Reviewed-by: Matthew Auld <matthew.a...@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210121232807.16618-1-ch...@chris-wilson.co.uk (cherry picked from commit 977a372e972cb42799746c284035a33c64ebace9) Signed-off-by: Jani Nikula <jani.nik...@intel.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c index 10a865f3dc09..9ed19b8bca60 100644 --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -631,24 +631,26 @@ static int flush_lazy_signals(struct i915_active *ref) int __i915_active_wait(struct i915_active *ref, int state) { - int err; - might_sleep(); - if (!i915_active_acquire_if_busy(ref)) - return 0; - /* Any fence added after the wait begins will not be auto-signaled */ - err = flush_lazy_signals(ref); - i915_active_release(ref); - if (err) - return err; + if (i915_active_acquire_if_busy(ref)) { + int err; - if (!i915_active_is_idle(ref) && - ___wait_var_event(ref, i915_active_is_idle(ref), - state, 0, 0, schedule())) - return -EINTR; + err = flush_lazy_signals(ref); + i915_active_release(ref); + if (err) + return err; + if (___wait_var_event(ref, i915_active_is_idle(ref), + state, 0, 0, schedule())) + return -EINTR; + } + + /* + * After the wait is complete, the caller may free the active. + * We have to flush any concurrent retirement before returning. + */ flush_work(&ref->work); return 0; }
