drm/i915/gt: Taint the reset mutex with the shrinker

Declare that, under extreme circumstances, the shrinker may need to wait
upon a request, in which case reset must not itself deadlock in order to
ensure forward progress of the driver. That is since the shrinker may
depend upon a reset, any reset cannot touch the shrinker.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201229141626.4773-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index 7583f16..e02775f 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -1394,6 +1394,17 @@ void intel_gt_init_reset(struct intel_gt *gt)
        mutex_init(&gt->reset.mutex);
        init_srcu_struct(&gt->reset.backoff_srcu);
 
+       /*
+        * While undesirable to wait inside the shrinker, complain anyway.
+        *
+        * If we have to wait during shrinking, we guarantee forward progress
+        * by forcing the reset. Therefore during the reset we must not
+        * re-enter the shrinker. By declaring that we take the reset mutex
+        * within the shrinker, we forbid ourselves from performing any
+        * fs-reclaim or taking related locks during reset.
+        */
+       i915_gem_shrinker_taints_mutex(gt->i915, &gt->reset.mutex);
+
        /* no GPU until we are ready! */
        __set_bit(I915_WEDGED, &gt->reset.flags);
 }