/* 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();

}

void uv__signal_cleanup(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_cleanup();

  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);

  if (handle != NULL && handle->signum == signum)

    return handle;

  return NULL;

}

static void uv__signal_handler(int signum) {

  uv__signal_msg_t msg;

  uv_signal_t* handle;

  int saved_errno;

  saved_errno = errno;

  memset(&msg, 0, sizeof msg);

  if (uv__signal_lock()) {

    errno = saved_errno;

    return;

  }

  for (handle = uv__signal_first_handle(signum);

       handle != NULL && handle->signum == signum;

       handle = RB_NEXT(uv__signal_tree_s, &uv__signal_tree, handle)) {

    int r;

    msg.signum = signum;

    msg.handle = handle;

    /* write() should be atomic for small data chunks, so the entire message

     * should be written at once. In theory the pipe could become full, in

     * which case the user is out of luck.

     */

    do {

      r = write(handle->loop->signal_pipefd[1], &msg, sizeof msg);

    } while (r == -1 && errno == EINTR);

    assert(r == sizeof msg ||

           (r == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)));

    if (r != -1)

      handle->caught_signals++;

  }

  uv__signal_unlock();

  errno = saved_errno;

}

static int uv__signal_register_handler(int signum, int oneshot) {

  /* When this function is called, the signal lock must be held. */

  struct sigaction sa;

  /* XXX use a separate signal stack? */

  memset(&sa, 0, sizeof(sa));

  if (sigfillset(&sa.sa_mask))

    abort();

  sa.sa_handler = uv__signal_handler;

  sa.sa_flags = SA_RESTART;

  if (oneshot)

    sa.sa_flags |= SA_RESETHAND;

  /* XXX save old action so we can restore it later on? */

  if (sigaction(signum, &sa, NULL))

    return UV__ERR(errno);

  return 0;

}

static void uv__signal_unregister_handler(int signum) {

  /* When this function is called, the signal lock must be held. */

  struct sigaction sa;

  memset(&sa, 0, sizeof(sa));

  sa.sa_handler = SIG_DFL;

  /* sigaction can only fail with EINVAL or EFAULT; an attempt to deregister a

   * signal implies that it was successfully registered earlier, so EINVAL

   * should never happen.

   */

  if (sigaction(signum, &sa, NULL))

    abort();

}

static int uv__signal_loop_once_init(uv_loop_t* loop) {

  int err;

  /* Return if already initialized. */

  if (loop->signal_pipefd[0] != -1)

    return 0;

  err = uv__make_pipe(loop->signal_pipefd, UV__F_NONBLOCK);

  if (err)

    return err;

  uv__io_init(&loop->signal_io_watcher,

              uv__signal_event,

              loop->signal_pipefd[0]);

  uv__io_start(loop, &loop->signal_io_watcher, POLLIN);

  return 0;

}

int uv__signal_loop_fork(uv_loop_t* loop) {

  uv__io_stop(loop, &loop->signal_io_watcher, POLLIN);

  uv__close(loop->signal_pipefd[0]);

  uv__close(loop->signal_pipefd[1]);

  loop->signal_pipefd[0] = -1;

  loop->signal_pipefd[1] = -1;

  return uv__signal_loop_once_init(loop);

}

void uv__signal_loop_cleanup(uv_loop_t* loop) {

  QUEUE* q;

  /* Stop all the signal watchers that are still attached to this loop. This

   * ensures that the (shared) signal tree doesn't contain any invalid entries

   * entries, and that signal handlers are removed when appropriate.

   * It's safe to use QUEUE_FOREACH here because the handles and the handle

   * queue are not modified by uv__signal_stop().

   */

  QUEUE_FOREACH(q, &loop->handle_queue) {

    uv_handle_t* handle = QUEUE_DATA(q, uv_handle_t, handle_queue);

    if (handle->type == UV_SIGNAL)

      uv__signal_stop((uv_signal_t*) handle);

  }

  if (loop->signal_pipefd[0] != -1) {

    uv__close(loop->signal_pipefd[0]);

    loop->signal_pipefd[0] = -1;

  }

  if (loop->signal_pipefd[1] != -1) {

    uv__close(loop->signal_pipefd[1]);

    loop->signal_pipefd[1] = -1;

  }

}

int uv_signal_init(uv_loop_t* loop, uv_signal_t* handle) {

  int err;

  err = uv__signal_loop_once_init(loop);

  if (err)

    return err;

  uv__handle_init(loop, (uv_handle_t*) handle, UV_SIGNAL);

  handle->signum = 0;

  handle->caught_signals = 0;

  handle->dispatched_signals = 0;

  return 0;

}

void uv__signal_close(uv_signal_t* handle) {

  uv__signal_stop(handle);

}

int uv_signal_start(uv_signal_t* handle, uv_signal_cb signal_cb, int signum) {

  return uv__signal_start(handle, signal_cb, signum, 0);

}

int uv_signal_start_oneshot(uv_signal_t* handle,

                            uv_signal_cb signal_cb,

                            int signum) {

  return uv__signal_start(handle, signal_cb, signum, 1);

}

static int uv__signal_start(uv_signal_t* handle,

                            uv_signal_cb signal_cb,

                            int signum,

                            int oneshot) {

  sigset_t saved_sigmask;

  int err;

  uv_signal_t* first_handle;

  assert(!uv__is_closing(handle));

  /* If the user supplies signum == 0, then return an error already. If the

   * signum is otherwise invalid then uv__signal_register will find out

   * eventually.

   */

  if (signum == 0)

    return UV_EINVAL;

  /* Short circuit: if the signal watcher is already watching {signum} don't

   * go through the process of deregistering and registering the handler.

   * Additionally, this avoids pending signals getting lost in the small

   * time frame that handle->signum == 0.

   */

  if (signum == handle->signum) {

    handle->signal_cb = signal_cb;

    return 0;

  }

  /* If the signal handler was already active, stop it first. */

  if (handle->signum != 0) {

    uv__signal_stop(handle);

  }

  uv__signal_block_and_lock(&saved_sigmask);

  /* If at this point there are no active signal watchers for this signum (in

   * any of the loops), it's time to try and register a handler for it here.

   * Also in case there's only one-shot handlers and a regular handler comes in.

   */

  first_handle = uv__signal_first_handle(signum);

  if (first_handle == NULL ||

      (!oneshot && (first_handle->flags & UV_SIGNAL_ONE_SHOT))) {

    err = uv__signal_register_handler(signum, oneshot);

    if (err) {

      /* Registering the signal handler failed. Must be an invalid signal. */

      uv__signal_unlock_and_unblock(&saved_sigmask);

      return err;

    }

  }

  handle->signum = signum;

  if (oneshot)

    handle->flags |= UV_SIGNAL_ONE_SHOT;

  RB_INSERT(uv__signal_tree_s, &uv__signal_tree, handle);

  uv__signal_unlock_and_unblock(&saved_sigmask);

  handle->signal_cb = signal_cb;

  uv__handle_start(handle);

  return 0;

}

static void uv__signal_event(uv_loop_t* loop,

                             uv__io_t* w,

                             unsigned int events) {

  uv__signal_msg_t* msg;

  uv_signal_t* handle;

  char buf[sizeof(uv__signal_msg_t) * 32];

  size_t bytes, end, i;

  int r;

  bytes = 0;

  end = 0;

  do {

    r = read(loop->signal_pipefd[0], buf + bytes, sizeof(buf) - bytes);

    if (r == -1 && errno == EINTR)

      continue;

    if (r == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {

      /* If there are bytes in the buffer already (which really is extremely

       * unlikely if possible at all) we can't exit the function here. We'll

       * spin until more bytes are read instead.

       */

      if (bytes > 0)

        continue;

      /* Otherwise, there was nothing there. */

      return;

    }

    /* Other errors really should never happen. */

    if (r == -1)

      abort();

    bytes += r;

    /* `end` is rounded down to a multiple of sizeof(uv__signal_msg_t). */

    end = (bytes / sizeof(uv__signal_msg_t)) * sizeof(uv__signal_msg_t);

    for (i = 0; i < end; i += sizeof(uv__signal_msg_t)) {

      msg = (uv__signal_msg_t*) (buf + i);

      handle = msg->handle;

      if (msg->signum == handle->signum) {

        assert(!(handle->flags & UV_HANDLE_CLOSING));

        handle->signal_cb(handle, handle->signum);

      }

      handle->dispatched_signals++;

      if (handle->flags & UV_SIGNAL_ONE_SHOT)

        uv__signal_stop(handle);

    }

    bytes -= end;

    /* If there are any "partial" messages left, move them to the start of the

     * the buffer, and spin. This should not happen.

     */

    if (bytes) {

      memmove(buf, buf + end, bytes);

      continue;

    }

  } while (end == sizeof buf);

}

static int uv__signal_compare(uv_signal_t* w1, uv_signal_t* w2) {

  int f1;

  int f2;

  /* Compare signums first so all watchers with the same signnum end up

   * adjacent.

   */

  if (w1->signum < w2->signum) return -1;

  if (w1->signum > w2->signum) return 1;

  /* Handlers without UV_SIGNAL_ONE_SHOT set will come first, so if the first

   * handler returned is a one-shot handler, the rest will be too.

   */

  f1 = w1->flags & UV_SIGNAL_ONE_SHOT;

  f2 = w2->flags & UV_SIGNAL_ONE_SHOT;

  if (f1 < f2) return -1;

  if (f1 > f2) return 1;

  /* Sort by loop pointer, so we can easily look up the first item after

   * { .signum = x, .loop = NULL }.

   */

  if (w1->loop < w2->loop) return -1;

  if (w1->loop > w2->loop) return 1;

  if (w1 < w2) return -1;

  if (w1 > w2) return 1;

  return 0;

}

int uv_signal_stop(uv_signal_t* handle) {

  assert(!uv__is_closing(handle));

  uv__signal_stop(handle);

  return 0;

}

static void uv__signal_stop(uv_signal_t* handle) {

  uv_signal_t* removed_handle;

  sigset_t saved_sigmask;

  uv_signal_t* first_handle;

  int rem_oneshot;

  int first_oneshot;

  int ret;

  /* If the watcher wasn't started, this is a no-op. */

  if (handle->signum == 0)

    return;

  uv__signal_block_and_lock(&saved_sigmask);

  removed_handle = RB_REMOVE(uv__signal_tree_s, &uv__signal_tree, handle);

  assert(removed_handle == handle);

  (void) removed_handle;

  /* Check if there are other active signal watchers observing this signal. If

   * not, unregister the signal handler.

   */

  first_handle = uv__signal_first_handle(handle->signum);

  if (first_handle == NULL) {

    uv__signal_unregister_handler(handle->signum);

  } else {

    rem_oneshot = handle->flags & UV_SIGNAL_ONE_SHOT;

    first_oneshot = first_handle->flags & UV_SIGNAL_ONE_SHOT;

    if (first_oneshot && !rem_oneshot) {

      ret = uv__signal_register_handler(handle->signum, 1);

      assert(ret == 0);

      (void)ret;

    }

  }

  uv__signal_unlock_and_unblock(&saved_sigmask);

  handle->signum = 0;

  uv__handle_stop(handle);

}