lkml.org 
[lkml]   [2005]   [Oct]   [15]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateSat, 15 Oct 2005 16:07:02 -0700 (PDT)
SubjectRe: Possible memory ordering bug in page reclaim?
From"David S. Miller" <>
From: Andrea Arcangeli <andrea@suse.de>
Date: Sat, 15 Oct 2005 22:07:01 +0200

> sure see alpha:
> 
> 	__asm__ __volatile__(
> 	"1:	ldq_l %0,%1\n"
> 	"	addq %0,%3,%2\n"
> 	"	addq %0,%3,%0\n"
> 	"	stq_c %0,%1\n"
> 	"	beq %0,2f\n"
> 	"	mb\n"
> 
> the memory barrier is applied way after the write is visible to other
> cpus, you can even get an irq before the mb and block there for some
> usec.

For atomic operations returning values, there must be a memory
barrier both before and after the atomic operation.  This is
defined in Documentation/atomic_ops.txt, so Alpha needs to be
fixed to add a memory barrier at the beginning of these
assembler sequences.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-10-15 23:09    [from the cache]
©2003-2008