/*
- * Copyright (C) 2004-2009 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2004-2013 Andre Noll <maan@systemlinux.org>
*
* Licensed under the GPL v2. For licencing details see COPYING.
*/
#include <signal.h>
#include <sys/types.h>
-#include <dirent.h>
#include "para.h"
#include "error.h"
* 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)
{
exit(EXIT_FAILURE);
}
-/*
- * just write one integer to signal pipe
- */
+/* Write the signal number to signal pipe. */
static void generic_signal_handler(int s)
{
+ /*
+ * 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))
+ if (ret == sizeof(int)) {
+ errno = save_errno;
return;
+ }
if (ret < 0)
PARA_EMERG_LOG("%s\n", strerror(errno));
else
}
/**
- * 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.
+ *
+ * This either succeeds or calls exit(EXIT_FAILURE).
*
- * It just calls \p para_reap_child() until there are no more children left to
- * reap.
+ * \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.
*
- * This should be called if the fd for the signal pipe is ready for reading.
+ * \param sig The signal to unblock.
*
- * \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.
+ * This function removes the given signal from the current set of blocked
+ * signals.
+ *
+ * \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;
}
projects / paraslash.git / blobdiff