Cleanup mmio coalescing functions
[qemu-kvm/fedora.git] / aio.c
blobdc9b85d1677364d70e3a5bbdc863016eba671af0
1 /*
2 * QEMU aio implementation
4 * Copyright IBM, Corp. 2008
6 * Authors:
7 * Anthony Liguori <aliguori@us.ibm.com>
9 * This work is licensed under the terms of the GNU GPL, version 2. See
10 * the COPYING file in the top-level directory.
14 #include "qemu-common.h"
15 #include "block.h"
16 #include "sys-queue.h"
17 #include "qemu_socket.h"
19 typedef struct AioHandler AioHandler;
21 /* The list of registered AIO handlers */
22 static LIST_HEAD(, AioHandler) aio_handlers;
24 /* This is a simple lock used to protect the aio_handlers list. Specifically,
25 * it's used to ensure that no callbacks are removed while we're walking and
26 * dispatching callbacks.
28 static int walking_handlers;
30 struct AioHandler
32 int fd;
33 IOHandler *io_read;
34 IOHandler *io_write;
35 AioFlushHandler *io_flush;
36 int deleted;
37 void *opaque;
38 LIST_ENTRY(AioHandler) node;
41 static AioHandler *find_aio_handler(int fd)
43 AioHandler *node;
45 LIST_FOREACH(node, &aio_handlers, node) {
46 if (node->fd == fd)
47 if (!node->deleted)
48 return node;
51 return NULL;
54 int qemu_aio_set_fd_handler(int fd,
55 IOHandler *io_read,
56 IOHandler *io_write,
57 AioFlushHandler *io_flush,
58 void *opaque)
60 AioHandler *node;
62 node = find_aio_handler(fd);
64 /* Are we deleting the fd handler? */
65 if (!io_read && !io_write) {
66 if (node) {
67 /* If the lock is held, just mark the node as deleted */
68 if (walking_handlers)
69 node->deleted = 1;
70 else {
71 /* Otherwise, delete it for real. We can't just mark it as
72 * deleted because deleted nodes are only cleaned up after
73 * releasing the walking_handlers lock.
75 LIST_REMOVE(node, node);
76 qemu_free(node);
79 } else {
80 if (node == NULL) {
81 /* Alloc and insert if it's not already there */
82 node = qemu_mallocz(sizeof(AioHandler));
83 node->fd = fd;
84 LIST_INSERT_HEAD(&aio_handlers, node, node);
86 /* Update handler with latest information */
87 node->io_read = io_read;
88 node->io_write = io_write;
89 node->io_flush = io_flush;
90 node->opaque = opaque;
93 qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
95 return 0;
98 void qemu_aio_flush(void)
100 AioHandler *node;
101 int ret;
103 do {
104 ret = 0;
107 * If there are pending emulated aio start them now so flush
108 * will be able to return 1.
110 qemu_aio_wait();
112 LIST_FOREACH(node, &aio_handlers, node) {
113 ret |= node->io_flush(node->opaque);
115 } while (ret > 0);
118 void qemu_aio_wait(void)
120 int ret;
122 if (qemu_bh_poll())
123 return;
125 do {
126 AioHandler *node;
127 fd_set rdfds, wrfds;
128 int max_fd = -1;
130 walking_handlers = 1;
132 FD_ZERO(&rdfds);
133 FD_ZERO(&wrfds);
135 /* fill fd sets */
136 LIST_FOREACH(node, &aio_handlers, node) {
137 /* If there aren't pending AIO operations, don't invoke callbacks.
138 * Otherwise, if there are no AIO requests, qemu_aio_wait() would
139 * wait indefinitely.
141 if (node->io_flush && node->io_flush(node->opaque) == 0)
142 continue;
144 if (!node->deleted && node->io_read) {
145 FD_SET(node->fd, &rdfds);
146 max_fd = MAX(max_fd, node->fd + 1);
148 if (!node->deleted && node->io_write) {
149 FD_SET(node->fd, &wrfds);
150 max_fd = MAX(max_fd, node->fd + 1);
154 walking_handlers = 0;
156 /* No AIO operations? Get us out of here */
157 if (max_fd == -1)
158 break;
160 /* wait until next event */
161 ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
162 if (ret == -1 && errno == EINTR)
163 continue;
165 /* if we have any readable fds, dispatch event */
166 if (ret > 0) {
167 walking_handlers = 1;
169 /* we have to walk very carefully in case
170 * qemu_aio_set_fd_handler is called while we're walking */
171 node = LIST_FIRST(&aio_handlers);
172 while (node) {
173 AioHandler *tmp;
175 if (!node->deleted &&
176 FD_ISSET(node->fd, &rdfds) &&
177 node->io_read) {
178 node->io_read(node->opaque);
180 if (!node->deleted &&
181 FD_ISSET(node->fd, &wrfds) &&
182 node->io_write) {
183 node->io_write(node->opaque);
186 tmp = node;
187 node = LIST_NEXT(node, node);
189 if (tmp->deleted) {
190 LIST_REMOVE(tmp, node);
191 qemu_free(tmp);
195 walking_handlers = 0;
197 } while (ret == 0);