Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | [PATCH] TRIVIAL I: 2.5.6-pre3. Documentation | Date | Thu, 07 Mar 2002 18:37:02 +1100 |
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Linus, please apply. atomic ops are *not* barriers any more.
Sebastian Wilhelmi <wilhelmi@ira.uka.de>: Re: Question on your "Unreliable Guide To Locking": > Yes, this is no longer true. The modern assumptions are that they are > not barriers.
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.6-pre3/Documentation/DocBook/kernel-locking.tmpl trivial-2.5.6-pre3/Documentation/DocBook/kernel-locking.tmpl --- linux-2.5.6-pre3/Documentation/DocBook/kernel-locking.tmpl Sun May 20 10:43:05 2001 +++ trivial-2.5.6-pre3/Documentation/DocBook/kernel-locking.tmpl Thu Mar 7 18:20:33 2002 @@ -788,8 +788,18 @@ </para> <para> - Note that the atomic operations are defined to act as both - read and write barriers on all platforms. + Note that the atomic operations do in general not act as memory + barriers. Instead you can insert a memory barrier before or + after <function>atomic_inc()</function> or + <function>atomic_dec()</function> by inserting + <function>smp_mb__before_atomic_inc()</function>, + <function>smp_mb__after_atomic_inc()</function>, + <function>smp_mb__before_atomic_dec()</function> or + <function>smp_mb__after_atomic_dec()</function> + respectively. The advantage of using those macros instead of + <function>smp_mb()</function> is, that they are cheaper on some + platforms. + <!-- Sebastian Wilhelmi <seppi@seppi.de> 2002-03-04 --> </para> </sect1> -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell. - 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/
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