From 4a16d072723b48699ea162da24eff05eba298834 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 22 Jan 2009 01:02:35 -0500 Subject: 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 --- lockfile.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'lockfile.c') diff --git a/lockfile.c b/lockfile.c index 8589155532..3cd57dc385 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) { remove_lock_file(); - signal(signo, SIG_DFL); + sigchain_pop(signo); raise(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); atexit(remove_lock_file); } lk->owner = getpid(); -- cgit v1.2.1