Merge branch 'for-3.18-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
Pull percpu fix from Tejun Heo: "This contains one patch to fix a race condition which can lead to percpu_ref using a percpu pointer which is corrupted with a set DEAD bit. The bug was introduced while separating out the ATOMIC mode flag from the DEAD flag. The fix is pretty straight forward. I just committed the patch to the percpu tree but am sending out the pull request early as I'll be on vacation for a week. The patch should be fairly safe and while the latency will be higher I'll be checking emails" * 'for-3.18-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: percpu-ref: fix DEAD flag contamination of percpu pointer
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9f2e0f6370
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@ -133,7 +133,13 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref,
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/* paired with smp_store_release() in percpu_ref_reinit() */
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smp_read_barrier_depends();
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if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))
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/*
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* Theoretically, the following could test just ATOMIC; however,
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* then we'd have to mask off DEAD separately as DEAD may be
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* visible without ATOMIC if we race with percpu_ref_kill(). DEAD
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* implies ATOMIC anyway. Test them together.
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*/
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if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC_DEAD))
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return false;
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*percpu_countp = (unsigned long __percpu *)percpu_ptr;
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