collectors: Check for NULL set of collectors.

[sliver-openvswitch.git] / lib / fatal-signal.c

diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index ff01136..8180521 100644 (file)
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -26,6 +26,9 @@
 #include "shash.h"
 #include "util.h"
 
+#define THIS_MODULE VLM_fatal_signal
+#include "vlog.h"
+
 /* Signals to catch. */
 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
 
@@ -57,7 +60,11 @@ static void call_hooks(int sig_nr);
 
 /* Registers 'hook' to be called when a process termination signal is raised.
  * If 'run_at_exit' is true, 'hook' is also called during normal process
- * termination, e.g. when exit() is called or when main() returns. */
+ * termination, e.g. when exit() is called or when main() returns.
+ *
+ * 'func' will be invoked from an asynchronous signal handler, so it must be
+ * written appropriately.  For example, it must not call most C library
+ * functions, including malloc() or free(). */
 void
 fatal_signal_add_hook(void (*func)(void *aux), void *aux, bool run_at_exit)
 {
@@ -204,12 +211,33 @@ fatal_signal_remove_file_to_unlink(const char *file)
     fatal_signal_unblock();
 }
 
+/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
+ * Returns 0 if successful, otherwise a positive errno value. */
+int
+fatal_signal_unlink_file_now(const char *file)
+{
+    int error = unlink(file) ? errno : 0;
+    if (error) {
+        VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error));
+    }
+
+    fatal_signal_remove_file_to_unlink(file);
+
+    return error;
+}
+
 static void
 unlink_files(void *aux UNUSED)
 {
     do_unlink_files(); 
 }
 
+/* This is a fatal_signal_add_hook() callback (via unlink_files()).  It will be
+ * invoked from an asynchronous signal handler, so it cannot call most C
+ * library functions (unlink() is an explicit exception, see
+ * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html).
+ * That includes free(), so it doesn't try to free the 'files' data
+ * structure. */
 static void
 do_unlink_files(void)
 {