diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-11-23 11:33:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-11-23 11:33:49 -0800 |
| commit | 9f2e0f6370b5f37cea3deee47299c8dfb0228eeb (patch) | |
| tree | 1f7d684f6e84876806fa1f3cc5fab7029d7cf0d3 /include | |
| parent | d038a63ace6cf2ce3aeafa741b73d542ffb65163 (diff) | |
| parent | 4aab3b5b3ccf94fc907e66233e6ca4d8675759a6 (diff) | |
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
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/percpu-refcount.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index d5c89e0dd0e6..51ce60c35f4c 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -133,7 +133,13 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref, /* paired with smp_store_release() in percpu_ref_reinit() */ smp_read_barrier_depends(); - if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC)) + /* + * Theoretically, the following could test just ATOMIC; however, + * then we'd have to mask off DEAD separately as DEAD may be + * visible without ATOMIC if we race with percpu_ref_kill(). DEAD + * implies ATOMIC anyway. Test them together. + */ + if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC_DEAD)) return false; *percpu_countp = (unsigned long __percpu *)percpu_ptr; |