X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=signal.c;h=3b202a2c8ba6a62b23fa46f7e99ed207c4f08750;hp=f9b95f9006dee9c9cd558bb39bc0cc6c90ca1bb1;hb=6bcd10bc4ada11a04bc2b7425afe5a8855592cd2;hpb=c839ef92e35d5604748aa4674b400156ff7baced diff --git a/signal.c b/signal.c index f9b95f90..3b202a2c 100644 --- a/signal.c +++ b/signal.c @@ -1,150 +1,228 @@ /* - * Copyright (C) 2004-2006 Andre Noll + * Copyright (C) 2004-2013 Andre Noll * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA. + * Licensed under the GPL v2. For licencing details see COPYING. */ -/** \file signal.c signal handling functions */ - +/** \file signal.c Signal handling functions. */ +#include +#include #include "para.h" +#include "error.h" #include "fd.h" -#include - -#include "error.h" static int signal_pipe[2]; /** - * initialize the paraslash signal subsystem + * Initialize the paraslash signal subsystem. * * This function creates a pipe, the signal pipe, to deliver pending * signals to the application (Bernstein's trick). It should be called * during the application's startup part, followed by subsequent calls * to para_install_sighandler() for each signal that should be caught. * - * para_signal_init() installs a generic signal handler which is used for all - * signals simultaneously. When a signal arrives, this generic signal handler - * writes the corresponding signal number to the signal pipe so that the - * application can test for pending signals simply by checking the signal pipe - * for reading, e.g. by using the select(2) system call. + * A generic signal handler is used for all signals simultaneously. When a + * signal arrives, the signal handler writes the number of the signal received + * to one end of the signal pipe. The application can test for pending signals + * by checking if the file descriptor of the other end of the signal pipe is + * ready for reading, see select(2). * - * \return This function either succeeds or calls exit(2) to terminate - * the current process. On success, the file descriptor of the signal pipe is - * returned. + * \return This function either succeeds or calls exit(2) to terminate the + * current process. On success, the file descriptor of the read end of the + * signal pipe is returned. */ int para_signal_init(void) { - int ret = -E_SIGNAL_PIPE; - if (pipe(signal_pipe)) + int ret; + if (pipe(signal_pipe) < 0) { + ret = -ERRNO_TO_PARA_ERROR(errno); goto err_out; - ret = mark_fd_nonblock(signal_pipe[0]); + } + ret = mark_fd_nonblocking(signal_pipe[0]); if (ret < 0) goto err_out; - ret = mark_fd_nonblock(signal_pipe[1]); + ret = mark_fd_nonblocking(signal_pipe[1]); if (ret < 0) goto err_out; return signal_pipe[0]; err_out: - PARA_EMERG_LOG("%s\n", PARA_STRERROR(-ret)); + PARA_EMERG_LOG("%s\n", para_strerror(-ret)); exit(EXIT_FAILURE); } -/* - * just write one integer to signal pipe - */ +/* Write the signal number to signal pipe. */ static void generic_signal_handler(int s) { - write(signal_pipe[1], &s, sizeof(int)); - //fprintf(stderr, "got sig %i, write returned %d\n", s, ret); + /* + * Signal handlers that make system calls must save a copy of errno on + * entry to the handler and restore it on exit, to prevent the + * possibility of overwriting a errno value that had previously been + * set in the main program. + */ + int save_errno = errno; + ssize_t ret = write(signal_pipe[1], &s, sizeof(int)); + + if (ret == sizeof(int)) { + errno = save_errno; + return; + } + if (ret < 0) + PARA_EMERG_LOG("%s\n", strerror(errno)); + else + PARA_EMERG_LOG("short write to signal pipe\n"); + exit(EXIT_FAILURE); } /** - * reap one child + * Reap one child. * - * call waitpid() and print a log message containing the pid - * and the cause of the child's death. + * \param pid In case a child died, its pid is returned here. * - * \return Like \p waitpid(), this function returns the process ID of the - * terminated child; on error, \p -E_WAITPID is returned. - * \sa waitpid(2) + * Call waitpid() and print a log message containing the pid and the cause of + * the child's death. + * + * \return A (negative) paraslash error code on errors, zero, if no child died, + * one otherwise. If and only if the function returns one, the content of \a + * pid is meaningful. + * + * \sa waitpid(2). */ -pid_t para_reap_child(void) +int para_reap_child(pid_t *pid) { int status; - pid_t pid = waitpid(-1, &status, WNOHANG); + *pid = waitpid(-1, &status, WNOHANG); - if (pid <= 0) { - if (pid < 0) - pid = -E_WAITPID; - return pid; - } + if (!*pid) + return 0; + if (*pid < 0) + return -ERRNO_TO_PARA_ERROR(errno); if (WIFEXITED(status)) - PARA_DEBUG_LOG("child %i exited. Exit status: %i\n", pid, + PARA_DEBUG_LOG("child %i exited. Exit status: %i\n", (int)*pid, WEXITSTATUS(status)); else if (WIFSIGNALED(status)) - PARA_DEBUG_LOG("child %i was killed by signal %i\n", pid, + PARA_DEBUG_LOG("child %i was killed by signal %i\n", (int)*pid, WTERMSIG(status)); else - PARA_WARNING_LOG("child %i terminated abormally\n", pid); - return pid; + PARA_WARNING_LOG("child %i terminated abormally\n", (int)*pid); + return 1; +} + +/** + * Install the given handler for the given signal. + * + * \param sig The number of the signal to catch. + * \param handler to be installed, \p SIG_IGN, or \p SIG_DFL. + * + * This either succeeds or calls exit(EXIT_FAILURE). + * + * \sa sigaction(2). + */ +void para_sigaction(int sig, void (*handler)(int)) +{ + struct sigaction act; + + PARA_DEBUG_LOG("catching signal %d\n", sig); + act.sa_handler = handler; + sigemptyset(&act.sa_mask); + act.sa_flags = 0; + if (sig == SIGALRM) { + #ifdef SA_INTERRUPT /* SunOS */ + act.sa_flags |= SA_INTERRUPT; + #endif + } else { + #ifdef SA_RESTART /* BSD */ + act.sa_flags |= SA_RESTART; + #endif + } + if (sigaction(sig, &act, NULL) >= 0) + return; + PARA_EMERG_LOG("failed to install signal handler for signal %d\n", + sig); + exit(EXIT_FAILURE); } /** - * paraslash's zombie killer + * Install the generic signal handler for the given signal number. + * + * \param sig The number of the signal to catch. * - * It just calls \p para_reap_child() until there are no more children left to - * reap. + * \sa signal(2), sigaction(2). */ -void para_reap_children(void) +void para_install_sighandler(int sig) { - while (para_reap_child() > 0) - ; /* nothing */ + para_sigaction(sig, &generic_signal_handler); } /** - * wrapper around signal(2) - * \param sig the number of the signal to catch + * Block a signal for the caller. * - * This installs the generic signal handler for the given signal. - * \return This function returns 1 on success and \p -E_SIGNAL_SIG_ERR on errors. - * \sa signal(2) + * \param sig The signal to block. + * + * This sets the given signal in the current signal mask of the calling process + * to prevent this signal from delivery. + * + * \sa \ref para_unblock_signal(), sigprocmask(2), sigaddset(3). */ -int para_install_sighandler(int sig) +void para_block_signal(int sig) { - PARA_DEBUG_LOG("catching signal %d\n", sig); - return signal(sig, &generic_signal_handler) == SIG_ERR? -E_SIGNAL_SIG_ERR : 1; + sigset_t set; + + PARA_DEBUG_LOG("blocking signal %d\n", sig); + sigemptyset(&set); + sigaddset(&set, sig); + sigprocmask(SIG_BLOCK, &set, NULL); } /** - * return number of next pending signal + * Unblock a signal. + * + * \param sig The signal to unblock. * - * This should be called if the fd for the signal pipe is ready for reading. + * This function removes the given signal from the current set of blocked + * signals. * - * \return On success, the number of the received signal is returned. \p - * -E_SIGNAL_READ is returned if a read error occured while reading the signal - * pipe. If the read was interrupted by another signal the function returns 0. + * \sa \ref para_block_signal(), sigprocmask(2), sigaddset(3). */ -int para_next_signal(void) +void para_unblock_signal(int sig) { - int s; - ssize_t r; + sigset_t set; - if ((r = read(signal_pipe[0], &s, sizeof(s)) == sizeof(s)) > 0) { - PARA_DEBUG_LOG("next signal: %d\n", s); - return s; + PARA_DEBUG_LOG("unblocking signal %d\n", sig); + sigemptyset(&set); + sigaddset(&set, sig); + sigprocmask(SIG_UNBLOCK, &set, NULL); +} + +/** + * Return the number of the next pending signal. + * + * \param rfds The fd_set containing the signal pipe. + * + * \return On success, the number of the received signal is returned. If there + * is no signal currently pending, the function returns zero. On read errors + * from the signal pipe, the process is terminated. + */ +int para_next_signal(fd_set *rfds) +{ + size_t n; + int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), rfds, &n); + + if (ret < 0) { + PARA_EMERG_LOG("%s\n", para_strerror(-ret)); + exit(EXIT_FAILURE); } - return r < 0 && (errno != EAGAIN)? 0 : -E_SIGNAL_READ; + if (n == 0) + return 0; + assert(n == sizeof(s)); + PARA_DEBUG_LOG("next signal: %d\n", s); + return s; +} + +/** + * Close the write end of the signal pipe. + */ +void para_signal_shutdown(void) +{ + close(signal_pipe[1]); }