X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=signal.c;h=3b202a2c8ba6a62b23fa46f7e99ed207c4f08750;hp=59a0d45aba7ad975fc287862308891435c4e9095;hb=6bcd10bc4ada11a04bc2b7425afe5a8855592cd2;hpb=b27f3e8dd53af7209626a9f0e98eb4770602c2e7

diff --git a/signal.c b/signal.c
index 59a0d45a..3b202a2c 100644
--- a/signal.c
+++ b/signal.c
@@ -1,5 +1,5 @@
 /*
- * 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.
  */
@@ -7,7 +7,6 @@
 
 #include <signal.h>
 #include <sys/types.h>
-#include <dirent.h>
 
 #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)
 {
@@ -52,15 +51,22 @@ 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)
 {
+	/*
+	 * 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
@@ -102,20 +108,6 @@ int para_reap_child(pid_t *pid)
 	return 1;
 }
 
-/**
- * Paraslash's zombie killer.
- *
- * It just calls \p para_reap_child() until there are no more children left to
- * reap.
- */
-void para_reap_children(void)
-{
-	pid_t pid;
-
-	while (para_reap_child(&pid) > 0)
-		; /* nothing */
-}
-
 /**
  * Install the given handler for the given signal.
  *
@@ -163,29 +155,66 @@ void para_install_sighandler(int sig)
 }
 
 /**
- * Return the number of next pending signal.
+ * Block a signal for the caller.
  *
- * This should be called if the fd for the signal pipe is ready for reading.
+ * \param sig The signal to block.
  *
- * \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 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_next_signal(void)
+void para_block_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("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 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;
 }