Re: SMP syncronization on AMD processors (broken?)

[Chuck Ebbert]

In-Reply-To: <434520FF.8050100@xxxxx>

On Thu, 06 Oct 2005 at 17:05:03 +0400, Kirill Korotaev wrote:

> The question is whether concurrent spin_lock()'s should 
> acquire it in more or less "fair" fashinon or one of CPUs can starve any 
> arbitrary time while others do reacquire it in a loop.

 You neglected to say what CPU type you compiled the kernel for.

 If it wasn't Pentium Pro maybe you could patch include/asm-i386/spinlock.h
line 82 (or the same place in x86-64) like this:

___
  * (PPro errata 66, 92)
  */
 
-#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
+#if 0
 
 #define __raw_spin_unlock_string \
         "movb $1,%0" \
___

The data might not make it out of the CPU write buffer without a locking
instruction doing the update.
__
Chuck
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