Commit 6cb0c6ad authored Aug 04, 2017 by Chris Wilson

drm/i915/shrinker: Wrap need_resched() inside preempt-disable



In order for us to successfully detect the end of a timeslice,
preemption must be disabled. Otherwise, inside the loop we may be
preempted many times without our noticing, and each time our timeslice
will be reset, invalidating need_resched()

Reported-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
Fixes: 290271de ("drm/i915: Spin for struct_mutex inside shrinker")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org> # v4.13-rc1+
Link: https://patchwork.freedesktop.org/patch/msgid/20170804104135.26805-1-chris@chris-wilson.co.uk


Tested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

parent 28152a23

drivers/gpu/drm/i915/i915_gem_shrinker.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -43,16 +43,21 @@ static bool shrinker_lock(struct drm_i915_private dev_priv, bool unlock)
		return true;

		case MUTEX_TRYLOCK_FAILED:
		*unlock = false;
		preempt_disable();
		do {
		cpu_relax();
		if (mutex_trylock(&dev_priv->drm.struct_mutex)) {
		case MUTEX_TRYLOCK_SUCCESS:
		*unlock = true;
		return true;
		break;
		}
		} while (!need_resched());
		preempt_enable();
		return *unlock;

		return false;
		case MUTEX_TRYLOCK_SUCCESS:
		*unlock = true;
		return true;
		}

		BUG();