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

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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: 290271de34 ("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>
This commit is contained in:
Chris Wilson 2017-08-04 11:41:35 +01:00
parent 28152a238b
commit 6cb0c6ad9e
1 changed files with 8 additions and 3 deletions
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11
drivers/gpu/drm/i915/i915_gem_shrinker.c
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@ -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();