On Fri, 2006-07-14 at 20:22 -0600, Matthew Wilcox wrote:
> On Fri, Jul 14, 2006 at 04:05:01PM -0400, Steven Rostedt wrote:
> > There are some more advanced barrier functions:
> >
> > (*) set_mb(var, value)
> > - (*) set_wmb(var, value)
> >
> > - These assign the value to the variable and then insert at least a write
> > - barrier after it, depending on the function. They aren't guaranteed to
> > + This assigns the value to the variable and then inserts at least a write
> > + barrier after it, depending on the function. It isn't guaranteed to
> > insert anything more than a compiler barrier in a UP compilation.
>
> "There is one more advanced barrier function"? ;-) Or did you want to
> remove set_mb()?
Actually below the patch area we still have:
(*) smp_mb__before_atomic_dec();
(*) smp_mb__after_atomic_dec();
(*) smp_mb__before_atomic_inc();
(*) smp_mb__after_atomic_inc();
So that "There are" references them too :)
>
> Plus, the "depending on the function" bit means "respectively". So what
> you really want as help is something like:
>
> This assigns the value to the variable and then inserts a
> barrier after the assignment. It isn't guaranteed to insert
> anything more than a compiler barrier in a UP compilation.
OK, you're right here, that "depending on the function" needs to go.
Here's a better version:
Thanks,
-- Steve
Signed-off-by: Steven Rostedt <[email protected]>
Index: linux-2.6.18-rc1/Documentation/memory-barriers.txt
===================================================================
--- linux-2.6.18-rc1.orig/Documentation/memory-barriers.txt 2006-07-14 15:38:23.000000000 -0400
+++ linux-2.6.18-rc1/Documentation/memory-barriers.txt 2006-07-14 22:31:01.000000000 -0400
@@ -1015,11 +1015,10 @@ CPU from reordering them.
There are some more advanced barrier functions:
(*) set_mb(var, value)
- (*) set_wmb(var, value)
- These assign the value to the variable and then insert at least a write
- barrier after it, depending on the function. They aren't guaranteed to
- insert anything more than a compiler barrier in a UP compilation.
+ This assigns the value to the variable and then inserts a memory barrier
+ after it. It isn't guaranteed to insert anything more than a compiler
+ barrier in a UP compilation.
(*) smp_mb__before_atomic_dec();
-
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