Commit 6cb0c6ad authored by Chris Wilson's avatar 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: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reported-by: default avatarTomi Sarvela <tomi.p.sarvela@intel.com>
Fixes: 290271de ("drm/i915: Spin for struct_mutex inside shrinker")
Signed-off-by: default avatarChris 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.ukTested-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
parent 28152a23
...@@ -43,16 +43,21 @@ static bool shrinker_lock(struct drm_i915_private *dev_priv, bool *unlock) ...@@ -43,16 +43,21 @@ static bool shrinker_lock(struct drm_i915_private *dev_priv, bool *unlock)
return true; return true;
case MUTEX_TRYLOCK_FAILED: case MUTEX_TRYLOCK_FAILED:
*unlock = false;
preempt_disable();
do { do {
cpu_relax(); cpu_relax();
if (mutex_trylock(&dev_priv->drm.struct_mutex)) { if (mutex_trylock(&dev_priv->drm.struct_mutex)) {
case MUTEX_TRYLOCK_SUCCESS:
*unlock = true; *unlock = true;
return true; break;
} }
} while (!need_resched()); } while (!need_resched());
preempt_enable();
return *unlock;
return false; case MUTEX_TRYLOCK_SUCCESS:
*unlock = true;
return true;
} }
BUG(); BUG();
......
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