compat/sys/buf_ring.h

120 	uint32_t cons_head, cons_next;
125 		cons_head = br->br_cons_head;
126 		cons_next = (cons_head + 1) & br->br_cons_mask;
128 		if (cons_head == br->br_prod_tail) {
132 	} while (!atomic_cmpset_acq_int(&br->br_cons_head, cons_head, cons_next));
134 	buf = br->br_ring[cons_head];
136 	br->br_ring[cons_head] = NULL;
143 	while (br->br_cons_tail != cons_head)
160 	uint32_t cons_head, cons_next;
180 	 *                                                                                cons_head = br->br_cons_head;
182 	 *                                                                                buf = br->br_ring[cons_head];     <see <1>>
186 	 *                                                                                if (cons_head == prod_tail)
190 	 * <1> Load (on core 1) from br->br_ring[cons_head] can be reordered (speculative readed) by CPU.
193 	cons_head = atomic_load_acq_32(&br->br_cons_head);
195 	cons_head = br->br_cons_head;
199 	cons_next = (cons_head + 1) & br->br_cons_mask;
201 	cons_next_next = (cons_head + 2) & br->br_cons_mask;
204 	if (cons_head == prod_tail)
215 	buf = br->br_ring[cons_head];
218 	br->br_ring[cons_head] = NULL;
221 	if (br->br_cons_tail != cons_head)
222 		panic("inconsistent list cons_tail=%d cons_head=%d",
223 		    br->br_cons_tail, cons_head);
237 	uint32_t cons_head, cons_next;
240 	cons_head = br->br_cons_head;
243 	cons_next = (cons_head + 1) & br->br_cons_mask;
244 	if (cons_head == prod_tail)
248 	br->br_ring[cons_head] = NULL;
322 	 * Single consumer, i.e. cons_head will not move while we are