diff options
| author | Grant Likely <grant.likely@secretlab.ca> | 2012-07-24 22:31:09 -0600 |
|---|---|---|
| committer | Grant Likely <grant.likely@secretlab.ca> | 2012-07-24 22:34:40 -0600 |
| commit | 6aeea3ecc33b1f36dbc3b80461d15a7052ae424f (patch) | |
| tree | bbd273e3e0ca76094aed8e9c77e5adfe2b07f779 /arch/x86/include/asm/bitops.h | |
| parent | 9844a5524ec532aee826c35e3031637c7fc8287b (diff) | |
| parent | bdc0077af574800d24318b6945cf2344e8dbb050 (diff) | |
Merge remote-tracking branch 'origin' into irqdomain/next
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) { |