mirror of
https://github.com/openvswitch/ovs
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268 lines
8.7 KiB
C
268 lines
8.7 KiB
C
/*
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* Copyright (c) 2008, 2009 Nicira Networks.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <config.h>
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#include "poll-loop.h"
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#include <assert.h>
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#include <errno.h>
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#include <poll.h>
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#include <stdlib.h>
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#include <string.h>
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#include "backtrace.h"
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#include "coverage.h"
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#include "dynamic-string.h"
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#include "list.h"
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#include "timeval.h"
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#define THIS_MODULE VLM_poll_loop
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#include "vlog.h"
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/* An event that will wake the following call to poll_block(). */
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struct poll_waiter {
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/* Set when the waiter is created. */
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struct list node; /* Element in global waiters list. */
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int fd; /* File descriptor. */
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short int events; /* Events to wait for (POLLIN, POLLOUT). */
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poll_fd_func *function; /* Callback function, if any, or null. */
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void *aux; /* Argument to callback function. */
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struct backtrace *backtrace; /* Optionally, event that created waiter. */
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/* Set only when poll_block() is called. */
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struct pollfd *pollfd; /* Pointer to element of the pollfds array
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(null if added from a callback). */
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};
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/* All active poll waiters. */
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static struct list waiters = LIST_INITIALIZER(&waiters);
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/* Number of elements in the waiters list. */
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static size_t n_waiters;
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/* Max time to wait in next call to poll_block(), in milliseconds, or -1 to
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* wait forever. */
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static int timeout = -1;
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/* Backtrace of 'timeout''s registration, if debugging is enabled. */
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static struct backtrace timeout_backtrace;
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/* Callback currently running, to allow verifying that poll_cancel() is not
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* being called on a running callback. */
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#ifndef NDEBUG
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static struct poll_waiter *running_cb;
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#endif
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static struct poll_waiter *new_waiter(int fd, short int events);
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/* Registers 'fd' as waiting for the specified 'events' (which should be POLLIN
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* or POLLOUT or POLLIN | POLLOUT). The following call to poll_block() will
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* wake up when 'fd' becomes ready for one or more of the requested events.
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*
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* The event registration is one-shot: only the following call to poll_block()
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* is affected. The event will need to be re-registered after poll_block() is
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* called if it is to persist. */
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struct poll_waiter *
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poll_fd_wait(int fd, short int events)
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{
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COVERAGE_INC(poll_fd_wait);
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return new_waiter(fd, events);
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}
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/* Causes the following call to poll_block() to block for no more than 'msec'
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* milliseconds. If 'msec' is nonpositive, the following call to poll_block()
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* will not block at all.
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*
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* The timer registration is one-shot: only the following call to poll_block()
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* is affected. The timer will need to be re-registered after poll_block() is
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* called if it is to persist. */
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void
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poll_timer_wait(int msec)
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{
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if (timeout < 0 || msec < timeout) {
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timeout = MAX(0, msec);
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if (VLOG_IS_DBG_ENABLED()) {
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backtrace_capture(&timeout_backtrace);
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}
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}
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}
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/* Causes the following call to poll_block() to wake up immediately, without
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* blocking. */
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void
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poll_immediate_wake(void)
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{
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poll_timer_wait(0);
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}
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static void PRINTF_FORMAT(2, 3)
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log_wakeup(const struct backtrace *backtrace, const char *format, ...)
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{
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struct ds ds;
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va_list args;
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ds_init(&ds);
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va_start(args, format);
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ds_put_format_valist(&ds, format, args);
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va_end(args);
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if (backtrace) {
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int i;
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ds_put_char(&ds, ':');
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for (i = 0; i < backtrace->n_frames; i++) {
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ds_put_format(&ds, " 0x%x", backtrace->frames[i]);
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}
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}
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VLOG_DBG("%s", ds_cstr(&ds));
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ds_destroy(&ds);
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}
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/* Blocks until one or more of the events registered with poll_fd_wait()
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* occurs, or until the minimum duration registered with poll_timer_wait()
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* elapses, or not at all if poll_immediate_wake() has been called.
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*
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* Also executes any autonomous subroutines registered with poll_fd_callback(),
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* if their file descriptors have become ready. */
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void
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poll_block(void)
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{
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static struct pollfd *pollfds;
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static size_t max_pollfds;
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struct poll_waiter *pw;
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struct list *node;
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int n_pollfds;
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int retval;
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assert(!running_cb);
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if (max_pollfds < n_waiters) {
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max_pollfds = n_waiters;
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pollfds = xrealloc(pollfds, max_pollfds * sizeof *pollfds);
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}
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n_pollfds = 0;
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LIST_FOR_EACH (pw, struct poll_waiter, node, &waiters) {
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pw->pollfd = &pollfds[n_pollfds];
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pollfds[n_pollfds].fd = pw->fd;
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pollfds[n_pollfds].events = pw->events;
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pollfds[n_pollfds].revents = 0;
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n_pollfds++;
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}
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if (!timeout) {
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COVERAGE_INC(poll_zero_timeout);
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}
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retval = time_poll(pollfds, n_pollfds, timeout);
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if (retval < 0) {
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static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
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VLOG_ERR_RL(&rl, "poll: %s", strerror(-retval));
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} else if (!retval && VLOG_IS_DBG_ENABLED()) {
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log_wakeup(&timeout_backtrace, "%d-ms timeout", timeout);
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}
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for (node = waiters.next; node != &waiters; ) {
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pw = CONTAINER_OF(node, struct poll_waiter, node);
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if (!pw->pollfd || !pw->pollfd->revents) {
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if (pw->function) {
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node = node->next;
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continue;
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}
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} else {
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if (VLOG_IS_DBG_ENABLED()) {
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log_wakeup(pw->backtrace, "%s%s%s%s%s on fd %d",
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pw->pollfd->revents & POLLIN ? "[POLLIN]" : "",
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pw->pollfd->revents & POLLOUT ? "[POLLOUT]" : "",
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pw->pollfd->revents & POLLERR ? "[POLLERR]" : "",
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pw->pollfd->revents & POLLHUP ? "[POLLHUP]" : "",
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pw->pollfd->revents & POLLNVAL ? "[POLLNVAL]" : "",
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pw->fd);
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}
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if (pw->function) {
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#ifndef NDEBUG
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running_cb = pw;
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#endif
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pw->function(pw->fd, pw->pollfd->revents, pw->aux);
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#ifndef NDEBUG
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running_cb = NULL;
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#endif
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}
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}
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node = node->next;
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poll_cancel(pw);
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}
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timeout = -1;
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timeout_backtrace.n_frames = 0;
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}
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/* Registers 'function' to be called with argument 'aux' by poll_block() when
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* 'fd' becomes ready for one of the events in 'events', which should be POLLIN
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* or POLLOUT or POLLIN | POLLOUT.
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*
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* The callback registration persists until the event actually occurs. At that
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* point, it is automatically de-registered. The callback function must
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* re-register the event by calling poll_fd_callback() again within the
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* callback, if it wants to be called back again later. */
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struct poll_waiter *
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poll_fd_callback(int fd, short int events, poll_fd_func *function, void *aux)
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{
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struct poll_waiter *pw = new_waiter(fd, events);
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pw->function = function;
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pw->aux = aux;
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return pw;
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}
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/* Cancels the file descriptor event registered with poll_fd_wait() or
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* poll_fd_callback(). 'pw' must be the struct poll_waiter returned by one of
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* those functions.
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*
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* An event registered with poll_fd_wait() may be canceled from its time of
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* registration until the next call to poll_block(). At that point, the event
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* is automatically canceled by the system and its poll_waiter is freed.
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*
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* An event registered with poll_fd_callback() may be canceled from its time of
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* registration until its callback is actually called. At that point, the
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* event is automatically canceled by the system and its poll_waiter is
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* freed. */
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void
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poll_cancel(struct poll_waiter *pw)
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{
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if (pw) {
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assert(pw != running_cb);
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list_remove(&pw->node);
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free(pw->backtrace);
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free(pw);
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n_waiters--;
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}
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}
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/* Creates and returns a new poll_waiter for 'fd' and 'events'. */
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static struct poll_waiter *
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new_waiter(int fd, short int events)
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{
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struct poll_waiter *waiter = xcalloc(1, sizeof *waiter);
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assert(fd >= 0);
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waiter->fd = fd;
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waiter->events = events;
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if (VLOG_IS_DBG_ENABLED()) {
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waiter->backtrace = xmalloc(sizeof *waiter->backtrace);
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backtrace_capture(waiter->backtrace);
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}
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list_push_back(&waiters, &waiter->node);
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n_waiters++;
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return waiter;
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}
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