path: root/lockfile.c
diff options
authorJeff King <>2009-01-22 06:02:35 (GMT)
committerJunio C Hamano <>2009-01-22 06:46:52 (GMT)
commit4a16d072723b48699ea162da24eff05eba298834 (patch)
tree04d834214e8448f254118278ec057c77e3f8f1f1 /lockfile.c
parent479b0ae81c9291a8bb8d7b2347cc58eeaa701304 (diff)
chain kill signals for cleanup functions
If a piece of code wanted to do some cleanup before exiting (e.g., cleaning up a lockfile or a tempfile), our usual strategy was to install a signal handler that did something like this: do_cleanup(); /* actual work */ signal(signo, SIG_DFL); /* restore previous behavior */ raise(signo); /* deliver signal, killing ourselves */ For a single handler, this works fine. However, if we want to clean up two _different_ things, we run into a problem. The most recently installed handler will run, but when it removes itself as a handler, it doesn't put back the first handler. This patch introduces sigchain, a tiny library for handling a stack of signal handlers. You sigchain_push each handler, and use sigchain_pop to restore whoever was before you in the stack. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'lockfile.c')
1 files changed, 7 insertions, 6 deletions
diff --git a/lockfile.c b/lockfile.c
index 8589155..3cd57dc 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -2,6 +2,7 @@
* Copyright (c) 2005, Junio C Hamano
#include "cache.h"
+#include "sigchain.h"
static struct lock_file *lock_file_list;
static const char *alternate_index_output;
@@ -24,7 +25,7 @@ static void remove_lock_file(void)
static void remove_lock_file_on_signal(int signo)
- signal(signo, SIG_DFL);
+ sigchain_pop(signo);
@@ -136,11 +137,11 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
if (0 <= lk->fd) {
if (!lock_file_list) {
- signal(SIGINT, remove_lock_file_on_signal);
- signal(SIGHUP, remove_lock_file_on_signal);
- signal(SIGTERM, remove_lock_file_on_signal);
- signal(SIGQUIT, remove_lock_file_on_signal);
- signal(SIGPIPE, remove_lock_file_on_signal);
+ sigchain_push(SIGINT, remove_lock_file_on_signal);
+ sigchain_push(SIGHUP, remove_lock_file_on_signal);
+ sigchain_push(SIGTERM, remove_lock_file_on_signal);
+ sigchain_push(SIGQUIT, remove_lock_file_on_signal);
+ sigchain_push(SIGPIPE, remove_lock_file_on_signal);
lk->owner = getpid();