X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=signal.c;h=32d6ab6624e5f493ac393b630a603c0968f11497;hp=3d1883f5f4b65f0c01b7b8944c6afbdb0d5f717c;hb=a1610c2bd6e3097c6473c5403bfd59425b2058ba;hpb=ff5830c9fc83ee59be9351c7ff45c1e376bac22b diff --git a/signal.c b/signal.c index 3d1883f5..32d6ab66 100644 --- a/signal.c +++ b/signal.c @@ -1,17 +1,17 @@ -/* - * Copyright (C) 2004-2006 Andre Noll - * - * Licensed under the GPL v2. For licencing details see COPYING. - */ -/** \file signal.c signal handling functions */ +/* Copyright (C) 2004 Andre Noll , see file COPYING. */ +/** \file signal.c Signal handling functions. */ #include #include -#include +#include #include "para.h" #include "error.h" #include "fd.h" +#include "list.h" +#include "string.h" +#include "sched.h" +#include "signal.h" static int signal_pipe[2]; @@ -21,21 +21,23 @@ static int signal_pipe[2]; * 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. + * to \ref 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(3) to terminate the + * current process. On success, a signal task structure is returned. */ -int para_signal_init(void) +struct signal_task *signal_init_or_die(void) { + struct signal_task *st; int ret; + + PARA_NOTICE_LOG("setting up signal handling\n"); if (pipe(signal_pipe) < 0) { ret = -ERRNO_TO_PARA_ERROR(errno); goto err_out; @@ -46,19 +48,35 @@ int para_signal_init(void) ret = mark_fd_nonblocking(signal_pipe[1]); if (ret < 0) goto err_out; - return signal_pipe[0]; + st = para_calloc(sizeof(*st)); + st->fd = signal_pipe[0]; + return st; 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); } /** @@ -73,7 +91,7 @@ static void generic_signal_handler(int s) * one otherwise. If and only if the function returns one, the content of \a * pid is meaningful. * - * \sa waitpid(2) + * \sa waitpid(2). */ int para_reap_child(pid_t *pid) { @@ -96,58 +114,123 @@ int para_reap_child(pid_t *pid) } /** - * Paraslash's zombie killer. + * Install the given handler for the given signal. * - * It just calls \p para_reap_child() until there are no more children left to - * reap. + * \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_reap_children(void) +void para_sigaction(int sig, void (*handler)(int)) { - pid_t pid; + struct sigaction act; - while (para_reap_child(&pid) > 0) - ; /* nothing */ + 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); } /** - * wrapper around signal(2) - * \param sig the number of the signal to catch + * Install the generic signal handler for the given signal number. * - * 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 number of the signal to catch. + * + * \sa signal(2), sigaction(2). */ -int para_install_sighandler(int sig) +void para_install_sighandler(int sig) { - PARA_DEBUG_LOG("catching signal %d\n", sig); - return signal(sig, &generic_signal_handler) == SIG_ERR? -E_SIGNAL_SIG_ERR : 1; + para_sigaction(sig, &generic_signal_handler); +} + +/** + * Block a signal for the caller. + * + * \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). + */ +void para_block_signal(int sig) +{ + sigset_t set; + + PARA_DEBUG_LOG("blocking signal %d\n", sig); + sigemptyset(&set); + sigaddset(&set, sig); + sigprocmask(SIG_BLOCK, &set, NULL); +} + +/** + * Unblock a signal. + * + * \param sig The signal to unblock. + * + * This function removes the given signal from the current set of blocked + * signals. + * + * \sa \ref para_block_signal(), sigprocmask(2), sigaddset(3). + */ +void para_unblock_signal(int sig) +{ + sigset_t set; + + PARA_DEBUG_LOG("unblocking signal %d\n", sig); + sigemptyset(&set); + sigaddset(&set, sig); + sigprocmask(SIG_UNBLOCK, &set, NULL); } /** - * return number of next pending signal + * Return the number of the next pending signal. * - * This should be called if the fd for the signal pipe is ready for reading. + * \param rfds The fd_set containing the signal pipe. * - * \return On success, the number of the received signal is returned. \p - * -E_SIGNAL_READ is returned if a read error occurred while reading the signal - * pipe. If the read was interrupted by another signal the function returns 0. + * \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(void) +int para_next_signal(fd_set *rfds) { - int s; - ssize_t r; + size_t n; + int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), rfds, &n); - if ((r = read(signal_pipe[0], &s, sizeof(s)) == sizeof(s)) > 0) { - PARA_DEBUG_LOG("next signal: %d\n", s); - return s; + 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 signal pipe. + * Close the write end of the signal pipe, deallocate resources. + * + * \param st The pointer obtained earlier from signal_init_or_die(). */ -void para_signal_shutdown(void) +void signal_shutdown(struct signal_task *st) { close(signal_pipe[1]); + free(st); }