- bump __FreeBSD version to reflect added buf_ring, memory barriers,

  and ifnet functions

- add memory barriers to <machine/atomic.h>
- update drivers to only conditionally define their own

- add lockless producer / consumer ring buffer
- remove ring buffer implementation from cxgb and update its callers

- add if_transmit(struct ifnet *ifp, struct mbuf *m) to ifnet to
  allow drivers to efficiently manage multiple hardware queues
  (i.e. not serialize all packets through one ifq)
- expose if_qflush to allow drivers to flush any driver managed queues

This work was supported by Bitgravity Inc. and Chelsio Inc.

1 files changed, 250 insertions, 0 deletions

diff --git a/sys/sys/buf_ring.h b/sys/sys/buf_ring.h
new file mode 100644
index 0000000..d77814a
--- /dev/null
+++ b/sys/sys/buf_ring.h
@@ -0,0 +1,250 @@
+/**************************************************************************
+ *
+ * Copyright (c) 2007,2008 Kip Macy kmacy@freebsd.org
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. The name of Kip Macy nor the names of other
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ *
+ ***************************************************************************/
+
+#ifndef	_SYS_BUF_RING_H_
+#define	_SYS_BUF_RING_H_
+
+#include <machine/cpu.h>
+
+#if defined(INVARIANTS) && !defined(DEBUG_BUFRING)
+#define DEBUG_BUFRING 1
+#endif
+
+#ifdef DEBUG_BUFRING
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#endif
+
+struct buf_ring {
+	volatile uint32_t	br_prod_head;
+	volatile uint32_t	br_prod_tail;	
+	int              	br_prod_size;
+	int              	br_prod_mask;
+	/*
+	 * Pad out to next L2 cache line
+	 */
+	uint64_t	  	_pad0[14];
+
+	volatile uint32_t	br_cons_head;
+	volatile uint32_t	br_cons_tail;
+	int		 	br_cons_size;
+	int              	br_cons_mask;
+	
+	/*
+	 * Pad out to next L2 cache line
+	 */
+	uint64_t	  	_pad1[14];
+#ifdef DEBUG_BUFRING
+	struct mtx		*br_lock;
+#endif	
+	void			*br_ring[0];
+};
+
+
+static __inline int
+buf_ring_enqueue(struct buf_ring *br, void *buf)
+{
+	uint32_t prod_head, prod_next;
+	uint32_t cons_tail;
+	int success;
+#ifdef DEBUG_BUFRING
+	int i;
+	for (i = br->br_cons_head; i != br->br_prod_head;
+	     i = ((i + 1) & br->br_cons_mask))
+		if(br->br_ring[i] == buf)
+			panic("buf=%p already enqueue at %d prod=%d cons=%d",
+			    buf, i, br->br_prod_tail, br->br_cons_tail);
+#endif	
+	critical_enter();
+	do {
+		prod_head = br->br_prod_head;
+		cons_tail = br->br_cons_tail;
+
+		prod_next = (prod_head + 1) & br->br_prod_mask;
+		
+		if (prod_next == cons_tail) {
+			critical_exit();
+			return (ENOSPC);
+		}
+		
+		success = atomic_cmpset_int(&br->br_prod_head, prod_head,
+		    prod_next);
+	} while (success == 0);
+#ifdef DEBUG_BUFRING
+	if (br->br_ring[prod_head] != NULL)
+		panic("dangling value in enqueue");
+#endif	
+	br->br_ring[prod_head] = buf;
+	wmb();
+
+	/*
+	 * If there are other enqueues in progress
+	 * that preceeded us, we need to wait for them
+	 * to complete 
+	 */   
+	while (br->br_prod_tail != prod_head)
+		cpu_spinwait();
+	br->br_prod_tail = prod_next;
+	mb();
+	critical_exit();
+	return (0);
+}
+
+/*
+ * multi-consumer safe dequeue 
+ *
+ */
+static __inline void *
+buf_ring_dequeue_mc(struct buf_ring *br)
+{
+	uint32_t cons_head, cons_next;
+	uint32_t prod_tail;
+	void *buf;
+	int success;
+
+	critical_enter();
+	do {
+		cons_head = br->br_cons_head;
+		prod_tail = br->br_prod_tail;
+
+		cons_next = (cons_head + 1) & br->br_cons_mask;
+		
+		if (cons_head == prod_tail) {
+			critical_exit();
+			return (NULL);
+		}
+		
+		success = atomic_cmpset_int(&br->br_cons_head, cons_head,
+		    cons_next);
+	} while (success == 0);		
+
+	buf = br->br_ring[cons_head];
+#ifdef DEBUG_BUFRING
+	br->br_ring[cons_head] = NULL;
+#endif
+	mb();
+	
+	/*
+	 * If there are other dequeues in progress
+	 * that preceeded us, we need to wait for them
+	 * to complete 
+	 */   
+	while (br->br_cons_tail != cons_head)
+		cpu_spinwait();
+
+	br->br_cons_tail = cons_next;
+	mb();
+	critical_exit();
+
+	return (buf);
+}
+
+/*
+ * Single-Consumer dequeue for uses where dequeue
+ * is protected by a lock
+ */
+static __inline void *
+buf_ring_dequeue_sc(struct buf_ring *br)
+{
+	uint32_t cons_head, cons_next;
+	uint32_t prod_tail;
+	void *buf;
+	
+	critical_enter();
+	cons_head = br->br_cons_head;
+	prod_tail = br->br_prod_tail;
+	
+	cons_next = (cons_head + 1) & br->br_cons_mask;
+		
+	if (cons_head == prod_tail) {
+		critical_exit();
+		return (NULL);
+	}
+	
+	br->br_cons_head = cons_next;
+	buf = br->br_ring[cons_head];
+	mb();
+	
+#ifdef DEBUG_BUFRING
+	br->br_ring[cons_head] = NULL;
+	if (!mtx_owned(br->br_lock))
+		panic("lock not held on single consumer dequeue");
+	if (br->br_cons_tail != cons_head)
+		panic("inconsistent list cons_tail=%d cons_head=%d",
+		    br->br_cons_tail, cons_head);
+#endif
+	br->br_cons_tail = cons_next;
+	mb();
+	critical_exit();
+	return (buf);
+}
+
+static __inline void *
+buf_ring_peek(struct buf_ring *br)
+{
+
+#ifdef DEBUG_BUFRING
+	if ((br->br_lock != NULL) && !mtx_owned(br->br_lock))
+		panic("lock not held on single consumer dequeue");
+#endif	
+	mb();
+	return (br->br_ring[br->br_cons_tail]);
+}
+
+static __inline int
+buf_ring_full(struct buf_ring *br)
+{
+
+	return (((br->br_prod_head + 1) & br->br_prod_mask) == br->br_cons_tail);
+}
+
+static __inline int
+buf_ring_empty(struct buf_ring *br)
+{
+
+	return (br->br_cons_head == br->br_prod_tail);
+}
+
+static __inline int
+buf_ring_count(struct buf_ring *br)
+{
+
+	return ((br->br_prod_size + br->br_prod_tail - br->br_cons_tail)
+	    & br->br_prod_mask);
+}
+
+struct buf_ring *buf_ring_alloc(int count, struct malloc_type *type, int flags,
+    struct mtx *);
+void buf_ring_free(struct buf_ring *br, struct malloc_type *type);
+
+
+
+#endif