X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=signal.c;h=3b202a2c8ba6a62b23fa46f7e99ed207c4f08750;hp=f8be2f4612002214f669fa74ce92390866b0dc90;hb=6bcd10bc4ada11a04bc2b7425afe5a8855592cd2;hpb=026b8a73a399d13ddb00bd96453747790b40d3ad diff --git a/signal.c b/signal.c index f8be2f46..3b202a2c 100644 --- a/signal.c +++ b/signal.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2004-2008 Andre Noll + * Copyright (C) 2004-2013 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ @@ -7,7 +7,6 @@ #include #include -#include #include "para.h" #include "error.h" @@ -23,15 +22,15 @@ static int signal_pipe[2]; * 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) { @@ -52,13 +51,27 @@ err_out: 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); } /** @@ -96,60 +109,112 @@ int para_reap_child(pid_t *pid) } /** - * Paraslash's zombie killer. + * 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. * - * It just calls \p para_reap_child() until there are no more children left to - * reap. + * 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). + * Install the generic signal handler for the given signal number. * * \param sig The number of the signal to catch. * - * This installs the generic signal handler for the given signal. + * \sa signal(2), sigaction(2). + */ +void para_install_sighandler(int sig) +{ + para_sigaction(sig, &generic_signal_handler); +} + +/** + * Block a signal for the caller. + * + * \param sig The signal to block. * - * \return This function returns 1 on success and \p -E_SIGNAL_SIG_ERR on errors. + * This sets the given signal in the current signal mask of the calling process + * to prevent this signal from delivery. * - * \sa signal(2). + * \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 the 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. If the - * read returned zero or was interrupted by another signal the function returns - * 0. Otherwise, a negative error value is returned. + * \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 = read(signal_pipe[0], &s, sizeof(s)); + sigset_t set; - if (!r) { - PARA_CRIT_LOG("read from signal pipe returned zero\n"); - return 0; - } - if (r < 0) { - if (errno == EAGAIN || errno == EINTR) - return 0; - return -ERRNO_TO_PARA_ERROR(errno); + 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); } - assert(r == sizeof(s)); + if (n == 0) + return 0; + assert(n == sizeof(s)); PARA_DEBUG_LOG("next signal: %d\n", s); return s; }