X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=signal.c;h=32d6ab6624e5f493ac393b630a603c0968f11497;hp=aa63c8b5461a9627c021a514b83b7c8ee1067067;hb=HEAD;hpb=3b447b02e2d74d596ecf6f5f764bf847653d407c

diff --git a/signal.c b/signal.c
index aa63c8b5..d9a6aa37 100644
--- a/signal.c
+++ b/signal.c
@@ -1,16 +1,17 @@
-/*
- * Copyright (C) 2004-2011 Andre Noll <maan@systemlinux.org>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2004 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 /** \file signal.c Signal handling functions. */
 
 #include <signal.h>
 #include <sys/types.h>
+#include <regex.h>
 
 #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];
 
@@ -20,21 +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.
  *
- * \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;
@@ -45,25 +48,37 @@ int para_signal_init(void)
 	ret = mark_fd_nonblocking(signal_pipe[1]);
 	if (ret < 0)
 		goto err_out;
-	return signal_pipe[0];
+	st = zalloc(sizeof(*st));
+	st->fd = signal_pipe[0];
+	return st;
 err_out:
 	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)
 {
+	/*
+	 * 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
-		PARA_EMERG_LOG("short write to signal pipe\n");
+	}
+	/*
+	 * This is a fatal error which should never happen. We must not call
+	 * PARA_XXX_LOG() here because this might acquire the log mutex which
+	 * is already taken by the main program if the interrupt occurs while a
+	 * log message is being printed. The mutex will not be released as long
+	 * as this signal handler is running, so a deadlock ensues.
+	 */
 	exit(EXIT_FAILURE);
 }
 
@@ -190,16 +205,14 @@ void para_unblock_signal(int sig)
 /**
  * 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)
+int para_next_signal(void)
 {
 	size_t n;
-	int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), rfds, &n);
+	int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), &n);
 
 	if (ret < 0) {
 		PARA_EMERG_LOG("%s\n", para_strerror(-ret));
@@ -213,9 +226,12 @@ int para_next_signal(fd_set *rfds)
 }
 
 /**
- * Close the write end of 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);
 }