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       1                 :            : /*
       2                 :            :  * Copyright (c) 2013 Nicira, Inc.
       3                 :            :  *
       4                 :            :  * Licensed under the Apache License, Version 2.0 (the "License");
       5                 :            :  * you may not use this file except in compliance with the License.
       6                 :            :  * You may obtain a copy of the License at:
       7                 :            :  *
       8                 :            :  *     http://www.apache.org/licenses/LICENSE-2.0
       9                 :            :  *
      10                 :            :  * Unless required by applicable law or agreed to in writing, software
      11                 :            :  * distributed under the License is distributed on an "AS IS" BASIS,
      12                 :            :  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      13                 :            :  * See the License for the specific language governing permissions and
      14                 :            :  * limitations under the License.
      15                 :            :  */
      16                 :            : 
      17                 :            : #include <config.h>
      18                 :            : 
      19                 :            : #include "latch.h"
      20                 :            : #include <errno.h>
      21                 :            : #include <poll.h>
      22                 :            : #include <unistd.h>
      23                 :            : #include "poll-loop.h"
      24                 :            : #include "socket-util.h"
      25                 :            : 
      26                 :            : /* Initializes 'latch' as initially unset. */
      27                 :            : void
      28                 :       5989 : latch_init(struct latch *latch)
      29                 :            : {
      30                 :       5989 :     xpipe_nonblocking(latch->fds);
      31                 :       5989 : }
      32                 :            : 
      33                 :            : /* Destroys 'latch'. */
      34                 :            : void
      35                 :       3116 : latch_destroy(struct latch *latch)
      36                 :            : {
      37                 :       3116 :     close(latch->fds[0]);
      38                 :       3116 :     close(latch->fds[1]);
      39                 :       3116 : }
      40                 :            : 
      41                 :            : /* Resets 'latch' to the unset state.  Returns true if 'latch' was previously
      42                 :            :  * set, false otherwise. */
      43                 :            : bool
      44                 :     231241 : latch_poll(struct latch *latch)
      45                 :            : {
      46                 :            :     char buffer[_POSIX_PIPE_BUF];
      47                 :            : 
      48                 :     231241 :     return read(latch->fds[0], buffer, sizeof buffer) > 0;
      49                 :            : }
      50                 :            : 
      51                 :            : /* Sets 'latch'.
      52                 :            :  *
      53                 :            :  * Calls are not additive: a single latch_poll() clears out any number of
      54                 :            :  * latch_set(). */
      55                 :            : void
      56                 :     121170 : latch_set(struct latch *latch)
      57                 :            : {
      58                 :     121170 :     ignore(write(latch->fds[1], "", 1));
      59                 :     121170 : }
      60                 :            : 
      61                 :            : /* Returns true if 'latch' is set, false otherwise.  Does not reset 'latch'
      62                 :            :  * to the unset state. */
      63                 :            : bool
      64                 :      86661 : latch_is_set(const struct latch *latch)
      65                 :            : {
      66                 :            :     struct pollfd pfd;
      67                 :            :     int retval;
      68                 :            : 
      69                 :      86661 :     pfd.fd = latch->fds[0];
      70                 :      86661 :     pfd.events = POLLIN;
      71                 :            :     do {
      72                 :      86661 :         retval = poll(&pfd, 1, 0);
      73 [ -  + ][ #  # ]:      86661 :     } while (retval < 0 && errno == EINTR);
      74                 :            : 
      75                 :      86661 :     return pfd.revents & POLLIN;
      76                 :            : }
      77                 :            : 
      78                 :            : /* Causes the next poll_block() to wake up when 'latch' is set.
      79                 :            :  *
      80                 :            :  * ('where' is used in debug logging.  Commonly one would use latch_wait() to
      81                 :            :  * automatically provide the caller's source file and line number for
      82                 :            :  * 'where'.) */
      83                 :            : void
      84                 :     306618 : latch_wait_at(const struct latch *latch, const char *where)
      85                 :            : {
      86                 :     306618 :     poll_fd_wait_at(latch->fds[0], POLLIN, where);
      87                 :     306619 : }