1 /**************************************************************************
3 * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
9 * 1. Redistributions of source code must retain the above copyright notice,
10 * this list of conditions and the following disclaimer.
12 * 2. The name of Kip Macy nor the names of other
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
30 ***************************************************************************/
32 #ifndef _SYS_BUF_RING_H_
33 #define _SYS_BUF_RING_H_
35 #include <machine/cpu.h>
37 #if defined(INVARIANTS) && !defined(DEBUG_BUFRING)
38 #define DEBUG_BUFRING 1
43 #include <sys/mutex.h>
47 volatile uint32_t br_prod_head;
48 volatile uint32_t br_prod_tail;
53 * Pad out to next L2 cache line
57 volatile uint32_t br_cons_head;
58 volatile uint32_t br_cons_tail;
63 * Pad out to next L2 cache line
73 * multi-producer safe lock-free ring buffer enqueue
77 buf_ring_enqueue(struct buf_ring *br, void *buf)
79 uint32_t prod_head, prod_next;
84 for (i = br->br_cons_head; i != br->br_prod_head;
85 i = ((i + 1) & br->br_cons_mask))
86 if(br->br_ring[i] == buf)
87 panic("buf=%p already enqueue at %d prod=%d cons=%d",
88 buf, i, br->br_prod_tail, br->br_cons_tail);
92 prod_head = br->br_prod_head;
93 cons_tail = br->br_cons_tail;
95 prod_next = (prod_head + 1) & br->br_prod_mask;
97 if (prod_next == cons_tail) {
102 success = atomic_cmpset_int(&br->br_prod_head, prod_head,
104 } while (success == 0);
106 if (br->br_ring[prod_head] != NULL)
107 panic("dangling value in enqueue");
109 br->br_ring[prod_head] = buf;
113 * If there are other enqueues in progress
114 * that preceeded us, we need to wait for them
117 while (br->br_prod_tail != prod_head)
119 br->br_prod_tail = prod_next;
126 * multi-consumer safe dequeue
129 static __inline void *
130 buf_ring_dequeue_mc(struct buf_ring *br)
132 uint32_t cons_head, cons_next;
139 cons_head = br->br_cons_head;
140 prod_tail = br->br_prod_tail;
142 cons_next = (cons_head + 1) & br->br_cons_mask;
144 if (cons_head == prod_tail) {
149 success = atomic_cmpset_int(&br->br_cons_head, cons_head,
151 } while (success == 0);
153 buf = br->br_ring[cons_head];
155 br->br_ring[cons_head] = NULL;
160 * If there are other dequeues in progress
161 * that preceeded us, we need to wait for them
164 while (br->br_cons_tail != cons_head)
167 br->br_cons_tail = cons_next;
175 * single-consumer dequeue
176 * use where dequeue is protected by a lock
177 * e.g. a network driver's tx queue lock
179 static __inline void *
180 buf_ring_dequeue_sc(struct buf_ring *br)
182 uint32_t cons_head, cons_next;
187 cons_head = br->br_cons_head;
188 prod_tail = br->br_prod_tail;
190 cons_next = (cons_head + 1) & br->br_cons_mask;
192 if (cons_head == prod_tail) {
197 br->br_cons_head = cons_next;
198 buf = br->br_ring[cons_head];
202 br->br_ring[cons_head] = NULL;
203 if (!mtx_owned(br->br_lock))
204 panic("lock not held on single consumer dequeue");
205 if (br->br_cons_tail != cons_head)
206 panic("inconsistent list cons_tail=%d cons_head=%d",
207 br->br_cons_tail, cons_head);
209 br->br_cons_tail = cons_next;
216 * return a pointer to the first entry in the ring
217 * without modifying it, or NULL if the ring is empty
218 * race-prone if not protected by a lock
220 static __inline void *
221 buf_ring_peek(struct buf_ring *br)
225 if ((br->br_lock != NULL) && !mtx_owned(br->br_lock))
226 panic("lock not held on single consumer dequeue");
229 if (br->br_cons_head == br->br_prod_tail)
232 return (br->br_ring[br->br_cons_head]);
236 buf_ring_full(struct buf_ring *br)
239 return (((br->br_prod_head + 1) & br->br_prod_mask) == br->br_cons_tail);
243 buf_ring_empty(struct buf_ring *br)
246 return (br->br_cons_head == br->br_prod_tail);
250 buf_ring_count(struct buf_ring *br)
253 return ((br->br_prod_size + br->br_prod_tail - br->br_cons_tail)
257 struct buf_ring *buf_ring_alloc(int count, struct malloc_type *type, int flags,
259 void buf_ring_free(struct buf_ring *br, struct malloc_type *type);