1 /* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
4 * We are making the OpenFlow specification and associated documentation
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35 #include "poll-loop.h"
44 #define THIS_MODULE VLM_poll_loop
47 /* An event that will wake the following call to poll_block(). */
49 /* Set when the waiter is created. */
50 struct list node; /* Element in global waiters list. */
51 int fd; /* File descriptor. */
52 short int events; /* Events to wait for (POLLIN, POLLOUT). */
53 poll_fd_func *function; /* Callback function, if any, or null. */
54 void *aux; /* Argument to callback function. */
56 /* Set only when poll_block() is called. */
57 struct pollfd *pollfd; /* Pointer to element of the pollfds array
58 (null if added from a callback). */
61 /* All active poll waiters. */
62 static struct list waiters = LIST_INITIALIZER(&waiters);
64 /* Number of elements in the waiters list. */
65 static size_t n_waiters;
67 /* Max time to wait in next call to poll_block(), in milliseconds, or -1 to
69 static int timeout = -1;
71 /* Callback currently running, to allow verifying that poll_cancel() is not
72 * being called on a running callback. */
74 static struct poll_waiter *running_cb;
77 static struct poll_waiter *new_waiter(int fd, short int events);
79 /* Registers 'fd' as waiting for the specified 'events' (which should be POLLIN
80 * or POLLOUT or POLLIN | POLLOUT). The following call to poll_block() will
81 * wake up when 'fd' becomes ready for one or more of the requested events.
83 * The event registration is one-shot: only the following call to poll_block()
84 * is affected. The event will need to be re-registered after poll_block() is
85 * called if it is to persist. */
87 poll_fd_wait(int fd, short int events)
89 return new_waiter(fd, events);
92 /* Causes the following call to poll_block() to block for no more than 'msec'
93 * milliseconds. If 'msec' is nonpositive, the following call to poll_block()
94 * will not block at all.
96 * The timer registration is one-shot: only the following call to poll_block()
97 * is affected. The timer will need to be re-registered after poll_block() is
98 * called if it is to persist. */
100 poll_timer_wait(int msec)
102 if (timeout < 0 || msec < timeout) {
103 timeout = MAX(0, msec);
107 /* Causes the following call to poll_block() to wake up immediately, without
110 poll_immediate_wake(void)
115 /* Blocks until one or more of the events registered with poll_fd_wait()
116 * occurs, or until the minimum duration registered with poll_timer_wait()
117 * elapses, or not at all if poll_immediate_wake() has been called.
119 * Also executes any autonomous subroutines registered with poll_fd_callback(),
120 * if their file descriptor have become ready. */
124 static struct pollfd *pollfds;
125 static size_t max_pollfds;
127 struct poll_waiter *pw;
133 if (max_pollfds < n_waiters) {
134 max_pollfds = n_waiters;
135 pollfds = xrealloc(pollfds, max_pollfds * sizeof *pollfds);
139 LIST_FOR_EACH (pw, struct poll_waiter, node, &waiters) {
140 pw->pollfd = &pollfds[n_pollfds];
141 pollfds[n_pollfds].fd = pw->fd;
142 pollfds[n_pollfds].events = pw->events;
143 pollfds[n_pollfds].revents = 0;
147 retval = time_poll(pollfds, n_pollfds, timeout);
149 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
150 VLOG_ERR_RL(&rl, "poll: %s", strerror(-retval));
153 for (node = waiters.next; node != &waiters; ) {
154 pw = CONTAINER_OF(node, struct poll_waiter, node);
155 if (!pw->pollfd || !pw->pollfd->revents) {
160 } else if (pw->function) {
164 pw->function(pw->fd, pw->pollfd->revents, pw->aux);
176 /* Registers 'function' to be called with argument 'aux' by poll_block() when
177 * 'fd' becomes ready for one of the events in 'events', which should be POLLIN
178 * or POLLOUT or POLLIN | POLLOUT.
180 * The callback registration persists until the event actually occurs. At that
181 * point, it is automatically de-registered. The callback function must
182 * re-register the event by calling poll_fd_callback() again within the
183 * callback, if it wants to be called back again later. */
185 poll_fd_callback(int fd, short int events, poll_fd_func *function, void *aux)
187 struct poll_waiter *pw = new_waiter(fd, events);
188 pw->function = function;
193 /* Cancels the file descriptor event registered with poll_fd_wait() or
194 * poll_fd_callback(). 'pw' must be the struct poll_waiter returned by one of
197 * An event registered with poll_fd_wait() may be canceled from its time of
198 * registration until the next call to poll_block(). At that point, the event
199 * is automatically canceled by the system and its poll_waiter is freed.
201 * An event registered with poll_fd_callback() may be canceled from its time of
202 * registration until its callback is actually called. At that point, the
203 * event is automatically canceled by the system and its poll_waiter is
206 poll_cancel(struct poll_waiter *pw)
209 assert(pw != running_cb);
210 list_remove(&pw->node);
216 /* Creates and returns a new poll_waiter for 'fd' and 'events'. */
217 static struct poll_waiter *
218 new_waiter(int fd, short int events)
220 struct poll_waiter *waiter = xcalloc(1, sizeof *waiter);
223 waiter->events = events;
224 list_push_back(&waiters, &waiter->node);