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/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "uv.h"
#include "internal.h"

#include <assert.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifndef SA_RESTART
# define SA_RESTART 0
#endif

typedef struct {
  uv_signal_t* handle;
  int signum;
} uv__signal_msg_t;

RB_HEAD(uv__signal_tree_s, uv_signal_s);


static int uv__signal_unlock(void);
static int uv__signal_start(uv_signal_t* handle,
                            uv_signal_cb signal_cb,
                            int signum,
                            int oneshot);
static void uv__signal_event(uv_loop_t* loop, uv__io_t* w, unsigned int events);
static int uv__signal_compare(uv_signal_t* w1, uv_signal_t* w2);
static void uv__signal_stop(uv_signal_t* handle);
static void uv__signal_unregister_handler(int signum);


static uv_once_t uv__signal_global_init_guard = UV_ONCE_INIT;
static struct uv__signal_tree_s uv__signal_tree =
    RB_INITIALIZER(uv__signal_tree);
static int uv__signal_lock_pipefd[2] = { -1, -1 };

RB_GENERATE_STATIC(uv__signal_tree_s,
                   uv_signal_s, tree_entry,
                   uv__signal_compare)

static void uv__signal_global_reinit(void);

static void uv__signal_global_init(void) {
  if (uv__signal_lock_pipefd[0] == -1)
    /* pthread_atfork can register before and after handlers, one
     * for each child. This only registers one for the child. That
     * state is both persistent and cumulative, so if we keep doing
     * it the handler functions will be called multiple times. Thus
     * we only want to do it once.
     */
    if (pthread_atfork(NULL, NULL, &uv__signal_global_reinit))
      abort();

  uv__signal_global_reinit();
}


UV_DESTRUCTOR(static void uv__signal_global_fini(void)) {
  /* We can only use signal-safe functions here.
   * That includes read/write and close, fortunately.
   * We do all of this directly here instead of resetting
   * uv__signal_global_init_guard because
   * uv__signal_global_once_init is only called from uv_loop_init
   * and this needs to function in existing loops.
   */
  if (uv__signal_lock_pipefd[0] != -1) {
    uv__close(uv__signal_lock_pipefd[0]);
    uv__signal_lock_pipefd[0] = -1;
  }

  if (uv__signal_lock_pipefd[1] != -1) {
    uv__close(uv__signal_lock_pipefd[1]);
    uv__signal_lock_pipefd[1] = -1;
  }
}


static void uv__signal_global_reinit(void) {
  uv__signal_global_fini();

  if (uv__make_pipe(uv__signal_lock_pipefd, 0))
    abort();

  if (uv__signal_unlock())
    abort();
}


void uv__signal_global_once_init(void) {
  uv_once(&uv__signal_global_init_guard, uv__signal_global_init);
}


static int uv__signal_lock(void) {
  int r;
  char data;

  do {
    r = read(uv__signal_lock_pipefd[0], &data, sizeof data);
  } while (r < 0 && errno == EINTR);

  return (r < 0) ? -1 : 0;
}


static int uv__signal_unlock(void) {
  int r;
  char data = 42;

  do {
    r = write(uv__signal_lock_pipefd[1], &data, sizeof data);
  } while (r < 0 && errno == EINTR);

  return (r < 0) ? -1 : 0;
}


static void uv__signal_block_and_lock(sigset_t* saved_sigmask) {
  sigset_t new_mask;

  if (sigfillset(&new_mask))
    abort();

  if (pthread_sigmask(SIG_SETMASK, &new_mask, saved_sigmask))
    abort();

  if (uv__signal_lock())
    abort();
}


static void uv__signal_unlock_and_unblock(sigset_t* saved_sigmask) {
  if (uv__signal_unlock())
    abort();

  if (pthread_sigmask(SIG_SETMASK, saved_sigmask, NULL))
    abort();
}


static uv_signal_t* uv__signal_first_handle(int signum) {
  /* This function must be called with the signal lock held. */
  uv_signal_t lookup;
  uv_signal_t* handle;

  lookup.signum = signum;
  lookup.flags = 0;
  lookup.loop = NULL;

  handle = RB_NFIND(uv__signal_tree_s, &uv__signal_tree, &lookup);