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| author | NeilBrown <neilb@suse.de> | 2012-08-01 20:40:02 +1000 |
|---|---|---|
| committer | NeilBrown <neilb@suse.de> | 2012-08-01 20:40:02 +1000 |
| commit | bb181e2e48f8c85db08c9cb015cbba9618dbf05c (patch) | |
| tree | 191bc24dd97bcb174535cc217af082f16da3b43d /arch/x86/include/asm/bitops.h | |
| parent | d57368afe63b3b7b45ce6c2b8c5276417935be2f (diff) | |
| parent | c039c332f23e794deb6d6f37b9f07ff3b27fb2cf (diff) | |
Merge commit 'c039c332f23e794deb6d6f37b9f07ff3b27fb2cf' into md
Pull in pre-requisites for adding raid10 support to dm-raid.
Diffstat (limited to 'arch/x86/include/asm/bitops.h')
| -rw-r--r-- | arch/x86/include/asm/bitops.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index a6983b27722..72f5009deb5 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -264,6 +264,13 @@ static inline int test_and_clear_bit(int nr, volatile unsigned long *addr) * This operation is non-atomic and can be reordered. * If two examples of this operation race, one can appear to succeed * but actually fail. You must protect multiple accesses with a lock. + * + * Note: the operation is performed atomically with respect to + * the local CPU, but not other CPUs. Portable code should not + * rely on this behaviour. + * KVM relies on this behaviour on x86 for modifying memory that is also + * accessed from a hypervisor on the same CPU if running in a VM: don't change + * this without also updating arch/x86/kernel/kvm.c */ static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr) { |