On Sat, Nov 16, 2013 at 11:58:45AM +0000, David Howells wrote:
> Paul E. McKenney <[email protected]> wrote:
>
> > - /* read index before reading contents at that index */
>
> > - smp_mb(); /* finish reading descriptor before incrementing tail
> > */
>
> I'd rather you didn't remove these comments (assuming they're correct) as
> they're pointing out the point of the example.
Ah, good point! I have added them back just before the smp_load_acquire()
and smp_store_release(), as shown below. Does that work?
Thanx, Paul
------------------------------------------------------------------------
diff --git a/Documentation/circular-buffers.txt
b/Documentation/circular-buffers.txt
index 15e54ff50018..88951b179262 100644
--- a/Documentation/circular-buffers.txt
+++ b/Documentation/circular-buffers.txt
@@ -200,6 +200,7 @@ The consumer will look something like this:
spin_lock(&consumer_lock);
+ /* Read index before reading contents at that index. */
unsigned long head = smp_load_acquire(buffer->head);
unsigned long tail = buffer->tail;
@@ -210,6 +211,7 @@ The consumer will look something like this:
consume_item(item);
+ /* Finish reading descriptor before incrementing tail. */
smp_store_release(buffer->tail,
(tail + 1) & (buffer->size - 1));
}
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