X-Git-Url: http://git.tuebingen.mpg.de/?p=dss.git;a=blobdiff_plain;f=sig.c;h=99d3dd34d7ca20c1018e8984d2a362906e07a42a;hp=9694684045145105001e7410b06558ee73bbfd39;hb=fafaa26953e4f452c6b91de4e24ec5ad2a8f6700;hpb=46cbddf465bd66ba1d5c4bcc780ae0d65abd7f73

diff --git a/sig.c b/sig.c
index 9694684..99d3dd3 100644
--- a/sig.c
+++ b/sig.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2004-2010 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2004-2010 Andre Noll <maan@tuebingen.mpg.de>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -23,6 +23,7 @@
 #include "log.h"
 #include "str.h"
 #include "file.h"
+#include "sig.h"
 
 static int signal_pipe[2];
 
@@ -59,16 +60,31 @@ int signal_init(void)
 		goto err_out;
 	return signal_pipe[0];
 err_out:
-	DSS_EMERG_LOG("%s\n", dss_strerror(-ret));
+	DSS_EMERG_LOG(("%s\n", dss_strerror(-ret)));
 	exit(EXIT_FAILURE);
 }
 
-/*
- * just write one integer to signal pipe
- */
+/* Write the signal number to the signal pipe, abort on errors. */
 static void generic_signal_handler(int s)
 {
-	write(signal_pipe[1], &s, sizeof(int));
+	/*
+	 * 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)
+		DSS_EMERG_LOG(("%s\n", strerror(errno)));
+	else
+		DSS_EMERG_LOG(("short write to signal pipe\n"));
+	exit(EXIT_FAILURE);
 }
 
 /**
@@ -94,13 +110,13 @@ int reap_child(pid_t *pid, int *status)
 	if (*pid < 0)
 		return -ERRNO_TO_DSS_ERROR(errno);
 	if (WIFEXITED(*status))
-		DSS_DEBUG_LOG("child %i exited. Exit status: %i\n", (int)*pid,
-			WEXITSTATUS(*status));
+		DSS_DEBUG_LOG(("child %i exited. Exit status: %i\n", (int)*pid,
+			WEXITSTATUS(*status)));
 	else if (WIFSIGNALED(*status))
-		DSS_DEBUG_LOG("child %i was killed by signal %i\n", (int)*pid,
-			WTERMSIG(*status));
+		DSS_DEBUG_LOG(("child %i was killed by signal %i\n", (int)*pid,
+			WTERMSIG(*status)));
 	else
-		DSS_WARNING_LOG("child %i terminated abormally\n", (int)*pid);
+		DSS_WARNING_LOG(("child %i terminated abormally\n", (int)*pid));
 	return 1;
 }
 
@@ -116,7 +132,7 @@ int reap_child(pid_t *pid, int *status)
  */
 int install_sighandler(int sig)
 {
-	DSS_DEBUG_LOG("catching signal %d\n", sig);
+	DSS_DEBUG_LOG(("catching signal %d\n", sig));
 	if (signal(sig, &generic_signal_handler) != SIG_ERR)
 		return 1;
 	return -E_SIGNAL_SIG_ERR;
@@ -138,14 +154,14 @@ int next_signal(void)
 
 	r = read(signal_pipe[0], &s, sizeof(s));
 	if (r == sizeof(s)) {
-		DSS_DEBUG_LOG("next signal: %d\n", s);
+		DSS_DEBUG_LOG(("next signal: %d\n", s));
 		return s;
 	}
 	err = errno;
 	assert(r < 0);
 	if (err == EAGAIN)
 		return 0;
-	DSS_ERROR_LOG("failed to read from signal pipe\n");
+	DSS_ERROR_LOG(("failed to read from signal pipe\n"));
 	return -ERRNO_TO_DSS_ERROR(err);
 }