fatal-signal: After fork, clear hooks instead of disabling them.

Until now, fatal_signal_fork() has simply disabled all the fatal signal
callback hooks.  This worked fine, because a daemon process forked only
once and the parent didn't do much before it exited.

But upcoming commits will introduce a --monitor option, which requires
processes to fork multiple times.  Sometimes the parent process will fork,
then run for a while, then fork again.  It's not good to disable the
hooks in the child process in such a case, because that prevents e.g.
pidfiles from being removed at the child's exit.

So this commit changes the semantics of fatal_signal_fork() to just
clearing out hooks.  After hooks are cleared, new hooks can be added and
will be executed on process termination in the usual way.

This commit also introduces a cancellation callback function so that a
canceled hook can free resources.

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/fatal-signal.h b/lib/fatal-signal.h
index a84d5fd71..94a1f1fb6 100644
--- a/lib/fatal-signal.h
+++ b/lib/fatal-signal.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,9 @@
 #include <stdbool.h>
 
 /* Basic interface. */
-void fatal_signal_add_hook(void (*)(void *aux), void *aux, bool run_at_exit);
+void fatal_signal_add_hook(void (*hook_cb)(void *aux),
+                           void (*cancel_cb)(void *aux), void *aux,
+                           bool run_at_exit);
 void fatal_signal_fork(void);
 void fatal_signal_run(void);
 void fatal_signal_wait(void);