2 * Copyright (C) 2004-2006 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
6 /** \file signal.c signal handling functions */
16 static int signal_pipe[2];
19 * initialize the paraslash signal subsystem
21 * This function creates a pipe, the signal pipe, to deliver pending
22 * signals to the application (Bernstein's trick). It should be called
23 * during the application's startup part, followed by subsequent calls
24 * to para_install_sighandler() for each signal that should be caught.
26 * para_signal_init() installs a generic signal handler which is used for all
27 * signals simultaneously. When a signal arrives, this generic signal handler
28 * writes the corresponding signal number to the signal pipe so that the
29 * application can test for pending signals simply by checking the signal pipe
30 * for reading, e.g. by using the select(2) system call.
32 * \return This function either succeeds or calls exit(2) to terminate
33 * the current process. On success, the file descriptor of the signal pipe is
36 int para_signal_init(void)
38 int ret = -E_SIGNAL_PIPE;
39 if (pipe(signal_pipe))
41 ret = mark_fd_nonblock(signal_pipe[0]);
44 ret = mark_fd_nonblock(signal_pipe[1]);
47 return signal_pipe[0];
49 PARA_EMERG_LOG("%s\n", PARA_STRERROR(-ret));
54 * just write one integer to signal pipe
56 static void generic_signal_handler(int s)
58 write(signal_pipe[1], &s, sizeof(int));
59 //fprintf(stderr, "got sig %i, write returned %d\n", s, ret);
65 * call waitpid() and print a log message containing the pid
66 * and the cause of the child's death.
68 * \return Like \p waitpid(), this function returns the process ID of the
69 * terminated child; on error, \p -E_WAITPID is returned.
72 pid_t para_reap_child(void)
75 pid_t pid = waitpid(-1, &status, WNOHANG);
82 if (WIFEXITED(status))
83 PARA_DEBUG_LOG("child %i exited. Exit status: %i\n", pid,
85 else if (WIFSIGNALED(status))
86 PARA_DEBUG_LOG("child %i was killed by signal %i\n", pid,
89 PARA_WARNING_LOG("child %i terminated abormally\n", pid);
94 * paraslash's zombie killer
96 * It just calls \p para_reap_child() until there are no more children left to
99 void para_reap_children(void)
101 while (para_reap_child() > 0)
106 * wrapper around signal(2)
107 * \param sig the number of the signal to catch
109 * This installs the generic signal handler for the given signal.
110 * \return This function returns 1 on success and \p -E_SIGNAL_SIG_ERR on errors.
113 int para_install_sighandler(int sig)
115 PARA_DEBUG_LOG("catching signal %d\n", sig);
116 return signal(sig, &generic_signal_handler) == SIG_ERR? -E_SIGNAL_SIG_ERR : 1;
120 * return number of next pending signal
122 * This should be called if the fd for the signal pipe is ready for reading.
124 * \return On success, the number of the received signal is returned. \p
125 * -E_SIGNAL_READ is returned if a read error occured while reading the signal
126 * pipe. If the read was interrupted by another signal the function returns 0.
128 int para_next_signal(void)
133 if ((r = read(signal_pipe[0], &s, sizeof(s)) == sizeof(s)) > 0) {
134 PARA_DEBUG_LOG("next signal: %d\n", s);
137 return r < 0 && (errno != EAGAIN)? 0 : -E_SIGNAL_READ;