x86: wmb() confusion in system.h

Comment says wmb is a nop, but it is implemented as lock addl
below... Should it be compiled to nop if we know we are running on
"good" Intel cpu?

At least remove confusing comment for now.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 9cff02ffe6c2d261e6c905fe6f0d9958ccaf2fbb..428d9471497fe8d679cc7679c0c6bbfd66f8ca0d 100644 (file)
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -296,16 +296,7 @@ void default_idle(void);
  */
 #ifdef CONFIG_X86_32
 /*
- * For now, "wmb()" doesn't actually do anything, as all
- * Intel CPU's follow what Intel calls a *Processor Order*,
- * in which all writes are seen in the program order even
- * outside the CPU.
- *
- * I expect future Intel CPU's to have a weaker ordering,
- * but I'd also expect them to finally get their act together
- * and add some real memory barriers if so.
- *
- * Some non intel clones support out of order store. wmb() ceases to be a
+ * Some non-Intel clones support out of order store. wmb() ceases to be a
  * nop for these.
  */
 #define mb() alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)