1 /**************************************************************************
3 * Copyright (c) 2007,2008 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
74 buf_ring_enqueue(struct buf_ring *br, void *buf)
76 uint32_t prod_head, prod_next;
81 for (i = br->br_cons_head; i != br->br_prod_head;
82 i = ((i + 1) & br->br_cons_mask))
83 if(br->br_ring[i] == buf)
84 panic("buf=%p already enqueue at %d prod=%d cons=%d",
85 buf, i, br->br_prod_tail, br->br_cons_tail);
89 prod_head = br->br_prod_head;
90 cons_tail = br->br_cons_tail;
92 prod_next = (prod_head + 1) & br->br_prod_mask;
94 if (prod_next == cons_tail) {
99 success = atomic_cmpset_int(&br->br_prod_head, prod_head,
101 } while (success == 0);
103 if (br->br_ring[prod_head] != NULL)
104 panic("dangling value in enqueue");
106 br->br_ring[prod_head] = buf;
110 * If there are other enqueues in progress
111 * that preceeded us, we need to wait for them
114 while (br->br_prod_tail != prod_head)
116 br->br_prod_tail = prod_next;
123 * multi-consumer safe dequeue
126 static __inline void *
127 buf_ring_dequeue_mc(struct buf_ring *br)
129 uint32_t cons_head, cons_next;
136 cons_head = br->br_cons_head;
137 prod_tail = br->br_prod_tail;
139 cons_next = (cons_head + 1) & br->br_cons_mask;
141 if (cons_head == prod_tail) {
146 success = atomic_cmpset_int(&br->br_cons_head, cons_head,
148 } while (success == 0);
150 buf = br->br_ring[cons_head];
152 br->br_ring[cons_head] = NULL;
157 * If there are other dequeues in progress
158 * that preceeded us, we need to wait for them
161 while (br->br_cons_tail != cons_head)
164 br->br_cons_tail = cons_next;
172 * Single-Consumer dequeue for uses where dequeue
173 * is protected by a lock
175 static __inline void *
176 buf_ring_dequeue_sc(struct buf_ring *br)
178 uint32_t cons_head, cons_next;
183 cons_head = br->br_cons_head;
184 prod_tail = br->br_prod_tail;
186 cons_next = (cons_head + 1) & br->br_cons_mask;
188 if (cons_head == prod_tail) {
193 br->br_cons_head = cons_next;
194 buf = br->br_ring[cons_head];
198 br->br_ring[cons_head] = NULL;
199 if (!mtx_owned(br->br_lock))
200 panic("lock not held on single consumer dequeue");
201 if (br->br_cons_tail != cons_head)
202 panic("inconsistent list cons_tail=%d cons_head=%d",
203 br->br_cons_tail, cons_head);
205 br->br_cons_tail = cons_next;
211 static __inline void *
212 buf_ring_peek(struct buf_ring *br)
216 if ((br->br_lock != NULL) && !mtx_owned(br->br_lock))
217 panic("lock not held on single consumer dequeue");
220 if (br->br_cons_head == br->br_prod_tail)
223 return (br->br_ring[br->br_cons_head]);
227 buf_ring_full(struct buf_ring *br)
230 return (((br->br_prod_head + 1) & br->br_prod_mask) == br->br_cons_tail);
234 buf_ring_empty(struct buf_ring *br)
237 return (br->br_cons_head == br->br_prod_tail);
241 buf_ring_count(struct buf_ring *br)
244 return ((br->br_prod_size + br->br_prod_tail - br->br_cons_tail)
248 struct buf_ring *buf_ring_alloc(int count, struct malloc_type *type, int flags,
250 void buf_ring_free(struct buf_ring *br, struct malloc_type *type);