svn commit: r191899 - head/sys/sys
Kip Macy
kmacy at FreeBSD.org
Thu May 7 19:57:14 UTC 2009
Author: kmacy
Date: Thu May 7 19:57:14 2009
New Revision: 191899
URL: http://svn.freebsd.org/changeset/base/191899
Log:
No man page currently exists so comment the two uncommented
non-trivial functions
Modified:
head/sys/sys/buf_ring.h
Modified: head/sys/sys/buf_ring.h
==============================================================================
--- head/sys/sys/buf_ring.h Thu May 7 19:46:29 2009 (r191898)
+++ head/sys/sys/buf_ring.h Thu May 7 19:57:14 2009 (r191899)
@@ -1,6 +1,6 @@
/**************************************************************************
*
- * Copyright (c) 2007,2008 Kip Macy kmacy at freebsd.org
+ * Copyright (c) 2007-2009 Kip Macy kmacy at freebsd.org
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -69,7 +69,10 @@ struct buf_ring {
void *br_ring[0];
};
-
+/*
+ * multi-producer safe lock-free ring buffer enqueue
+ *
+ */
static __inline int
buf_ring_enqueue(struct buf_ring *br, void *buf)
{
@@ -169,8 +172,9 @@ buf_ring_dequeue_mc(struct buf_ring *br)
}
/*
- * Single-Consumer dequeue for uses where dequeue
- * is protected by a lock
+ * single-consumer dequeue
+ * use where dequeue is protected by a lock
+ * e.g. a network driver's tx queue lock
*/
static __inline void *
buf_ring_dequeue_sc(struct buf_ring *br)
@@ -208,6 +212,11 @@ buf_ring_dequeue_sc(struct buf_ring *br)
return (buf);
}
+/*
+ * return a pointer to the first entry in the ring
+ * without modifying it, or NULL if the ring is empty
+ * race-prone if not protected by a lock
+ */
static __inline void *
buf_ring_peek(struct buf_ring *br)
{
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