1 /* Copyright (c) 2015 Oracle and/or its affiliates. All rights reserved.
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License, version 2.0,
5 as published by the Free Software Foundation.
6
7 This program is also distributed with certain software (including
8 but not limited to OpenSSL) that is licensed under separate terms,
9 as designated in a particular file or component or in included license
10 documentation. The authors of MySQL hereby grant you an additional
11 permission to link the program and your derivative works with the
12 separately licensed software that they have included with MySQL.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License, version 2.0, for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
22
23 #include "mysqld_daemon.h"
24 #include "mysqld.h"
25 #include "log.h"
26
27 #include <unistd.h>
28 #ifdef HAVE_SYS_WAIT_H
29 #include <sys/wait.h>
30 #endif
31
32 /**
33 Daemonize mysqld.
34
35 This function does sysv style of daemonization of mysqld.
36
37 @return - returns write end of the pipe file descriptor
38 which is used to notify the parent to exit.
39 */
mysqld_daemonize()40 int mysqld::runtime::mysqld_daemonize()
41 {
42 int pipe_fd[2];
43 if (pipe(pipe_fd) < 0)
44 return -1;
45
46 pid_t pid= fork();
47 if (pid == -1)
48 {
49 // Error
50 close(pipe_fd[0]);
51 close(pipe_fd[1]);
52 return -1;
53 }
54
55 if (pid != 0)
56 {
57 // Parent, close write end of pipe.
58 close(pipe_fd[1]);
59
60 // Wait for first child to fork successfully.
61 int rc,status;
62 char waitstatus;
63 while ((rc= waitpid(pid, &status, 0)) == -1 &&
64 errno == EINTR)
65 {
66 // Retry if errno is EINTR.
67 }
68 if (rc == -1)
69 {
70 fprintf(stderr, "Unable to wait for process %lld\n",
71 static_cast<long long>(pid));
72 close(pipe_fd[0]);
73 close(pipe_fd[1]);
74 return -1;
75 }
76
77 // Exit parent on signal from grand child
78 rc= read(pipe_fd[0], &waitstatus, 1);
79 close(pipe_fd[0]);
80
81 if (rc != 1)
82 {
83 fprintf(stderr, "Unable to determine if daemon is running: %s\n",
84 strerror(errno));
85 exit(MYSQLD_ABORT_EXIT);
86 }
87 else if (waitstatus != 1)
88 {
89 fprintf(stderr, "Initialization of mysqld failed: %d\n", waitstatus);
90 exit(MYSQLD_ABORT_EXIT);
91 }
92 _exit(MYSQLD_SUCCESS_EXIT);
93 }
94 else
95 {
96 // Child, close read end of pipe file descriptor.
97 close(pipe_fd[0]);
98
99 int stdinfd;
100 if ((stdinfd= open("/dev/null", O_RDONLY)) <= STDERR_FILENO)
101 {
102 close(pipe_fd[1]);
103 exit(MYSQLD_ABORT_EXIT);
104 }
105
106 if (! (dup2(stdinfd, STDIN_FILENO) != STDIN_FILENO)
107 && (setsid() > -1))
108 {
109 close(stdinfd);
110 pid_t grand_child_pid= fork();
111 switch (grand_child_pid)
112 {
113 case 0: // Grand child
114 return pipe_fd[1];
115 case -1:
116 close(pipe_fd[1]);
117 _exit(MYSQLD_FAILURE_EXIT);
118 default:
119 _exit(MYSQLD_SUCCESS_EXIT);
120 }
121 }
122 else
123 {
124 close(stdinfd);
125 close(pipe_fd[1]);
126 _exit(MYSQLD_SUCCESS_EXIT);
127 }
128 }
129 }
130
131 /**
132 Signal parent to exit.
133
134 @param pipe_write_fd File Descriptor of write end of pipe.
135
136 @param status status of the initialization done by grand child.
137 1 means initialization complete and the server
138 is ready to accept client connections.
139 0 means intialization aborted due to some failure.
140
141 @note This function writes the status to write end of pipe.
142 This notifies the parent which is block on read end of pipe.
143 */
signal_parent(int pipe_write_fd,char status)144 void mysqld::runtime::signal_parent(int pipe_write_fd, char status)
145 {
146 if (pipe_write_fd != -1)
147 {
148 while (write(pipe_write_fd, &status, 1) == -1 && errno == EINTR)
149 {
150 // Retry write syscall if errno is EINTR.
151 }
152
153 close(pipe_write_fd);
154 }
155 }
156