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yaml --- r: 315854 b: refs/heads/master c: d0a69d6 h: refs/heads/master v: v3
git-mirror · Jun 25, 2012 · cf0eda6 · cf0eda6
1 parent c5ffd87
commit cf0eda6
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Showing 2 changed files with 8 additions and 1 deletion.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ab9cf4996bb989983e73da894b8dd0239aa2c3c2
+refs/heads/master: d0a69d6321ca759bb8d47803d06ba8571ab42d07
diff --git a/trunk/arch/x86/include/asm/bitops.h b/trunk/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)
 {