Eric Lee / smarc-ti-linux-kernel

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Commit 9f2e0f6370b5f37cea3deee47299c8dfb0228eeb

Authored by Linus Torvalds
2 parents d038a63ace 4aab3b5b3c
Exists in ti-lsk-linux-4.1.y and in 10 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04

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

Showing 1 changed file Side-by-side Diff

include/linux/percpu-refcount.h
Diff comments   View file @ 9f2e0f6
... ... @@ -133,7 +133,13 @@
133 133 /* paired with smp_store_release() in percpu_ref_reinit() */
134 134 smp_read_barrier_depends();
135 135  
136   - if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))
  136 + /*
  137 + * Theoretically, the following could test just ATOMIC; however,
  138 + * then we'd have to mask off DEAD separately as DEAD may be
  139 + * visible without ATOMIC if we race with percpu_ref_kill(). DEAD
  140 + * implies ATOMIC anyway. Test them together.
  141 + */
  142 + if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC_DEAD))
137 143 return false;
138 144  
139 145 *percpu_countp = (unsigned long __percpu *)percpu_ptr;