| 1 | /* |
| 2 | * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com> |
| 3 | * Copyright (C) 2014 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License, version 2 only, as |
| 7 | * published by the Free Software Foundation. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, but WITHOUT |
| 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| 12 | * more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License along with |
| 15 | * this program; if not, write to the Free Software Foundation, Inc., 51 |
| 16 | * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| 17 | */ |
| 18 | |
| 19 | #define _LGPL_SOURCE |
| 20 | #include <unistd.h> |
| 21 | #include <common/compat/paths.h> |
| 22 | #include <fcntl.h> |
| 23 | #include <sys/wait.h> |
| 24 | #include <stdlib.h> |
| 25 | |
| 26 | #include <urcu/system.h> |
| 27 | |
| 28 | #include <common/daemonize.h> |
| 29 | #include <common/error.h> |
| 30 | |
| 31 | LTTNG_HIDDEN |
| 32 | int lttng_daemonize(pid_t *child_ppid, int *completion_flag, |
| 33 | int close_fds) |
| 34 | { |
| 35 | int ret; |
| 36 | pid_t pid; |
| 37 | |
| 38 | /* Get parent pid of this process. */ |
| 39 | *child_ppid = getppid(); |
| 40 | |
| 41 | pid = fork(); |
| 42 | if (pid < 0) { |
| 43 | PERROR("fork"); |
| 44 | goto error; |
| 45 | } else if (pid == 0) { |
| 46 | int fd; |
| 47 | pid_t sid; |
| 48 | |
| 49 | /* Child */ |
| 50 | |
| 51 | /* |
| 52 | * Get the newly created parent pid so we can signal |
| 53 | * that process when we are ready to operate. |
| 54 | */ |
| 55 | *child_ppid = getppid(); |
| 56 | |
| 57 | sid = setsid(); |
| 58 | if (sid < 0) { |
| 59 | PERROR("setsid"); |
| 60 | goto error; |
| 61 | } |
| 62 | |
| 63 | /* |
| 64 | * Try to change directory to /. If we can't well at |
| 65 | * least notify. |
| 66 | */ |
| 67 | ret = chdir("/"); |
| 68 | if (ret < 0) { |
| 69 | PERROR("chdir"); |
| 70 | } |
| 71 | |
| 72 | if (close_fds) { |
| 73 | fd = open(_PATH_DEVNULL, O_RDWR, 0); |
| 74 | if (fd < 0) { |
| 75 | PERROR("open %s", _PATH_DEVNULL); |
| 76 | /* |
| 77 | * Let 0, 1 and 2 open since we can't |
| 78 | * bind them to /dev/null. |
| 79 | */ |
| 80 | } else { |
| 81 | (void) dup2(fd, STDIN_FILENO); |
| 82 | (void) dup2(fd, STDOUT_FILENO); |
| 83 | (void) dup2(fd, STDERR_FILENO); |
| 84 | if (fd > 2) { |
| 85 | ret = close(fd); |
| 86 | if (ret < 0) { |
| 87 | PERROR("close"); |
| 88 | } |
| 89 | } |
| 90 | } |
| 91 | } |
| 92 | goto end; |
| 93 | } else { |
| 94 | /* Parent */ |
| 95 | |
| 96 | /* |
| 97 | * Waiting for child to notify this parent that it can |
| 98 | * exit. Note that sleep() is interrupted before the 1 |
| 99 | * second delay as soon as the signal is received, so it |
| 100 | * will not cause visible delay for the user. |
| 101 | */ |
| 102 | while (!CMM_LOAD_SHARED(*completion_flag)) { |
| 103 | int status; |
| 104 | pid_t ret; |
| 105 | |
| 106 | /* |
| 107 | * Check if child exists without blocking. If |
| 108 | * so, we have to stop this parent process and |
| 109 | * return an error. |
| 110 | */ |
| 111 | ret = waitpid(pid, &status, WNOHANG); |
| 112 | if (ret < 0 || (ret != 0 && WIFEXITED(status))) { |
| 113 | /* The child exited somehow or was not valid. */ |
| 114 | goto error; |
| 115 | } |
| 116 | sleep(1); |
| 117 | } |
| 118 | |
| 119 | /* |
| 120 | * From this point on, the parent can exit and the child |
| 121 | * is now an operationnal session daemon ready to serve |
| 122 | * clients and applications. |
| 123 | */ |
| 124 | exit(EXIT_SUCCESS); |
| 125 | } |
| 126 | |
| 127 | end: |
| 128 | return 0; |
| 129 | |
| 130 | error: |
| 131 | return -1; |
| 132 | } |