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 <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Jan 22, 2009 at 01:02 UTC
4a16d072723b48699ea162da24eff05eba298834
12 files changed
+125
-19
.gitignore
+1
@@ -152,6 +152,7 @@ test-match-trees
152
test-parse-options
153
test-path-utils
154
test-sha1
155
+test-sigchain
156
common-cmds.h
157
*.tar.gz
158
*.dsc
Makefile
+3
@@ -388,6 +388,7 @@ LIB_H += revision.h
388
LIB_H += run-command.h
389
LIB_H += sha1-lookup.h
390
LIB_H += sideband.h
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+LIB_H += sigchain.h
392
LIB_H += strbuf.h
393
LIB_H += tag.h
394
LIB_H += transport.h
@@ -481,6 +482,7 @@ LIB_OBJS += sha1-lookup.o
482
LIB_OBJS += sha1_name.o
483
LIB_OBJS += shallow.o
484
LIB_OBJS += sideband.o
485
+LIB_OBJS += sigchain.o
486
LIB_OBJS += strbuf.o
487
LIB_OBJS += symlinks.o
488
LIB_OBJS += tag.o
@@ -1364,6 +1366,7 @@ TEST_PROGRAMS += test-match-trees$X
1366
TEST_PROGRAMS += test-parse-options$X
1367
TEST_PROGRAMS += test-path-utils$X
1368
TEST_PROGRAMS += test-sha1$X
1369
+TEST_PROGRAMS += test-sigchain$X
1370
1371
all:: $(TEST_PROGRAMS)
1372
builtin-clone.c
+3
-2
@@ -19,6 +19,7 @@
19
#include "strbuf.h"
20
#include "dir.h"
21
#include "pack-refs.h"
22
+#include "sigchain.h"
23
24
/*
25
* Overall FIXMEs:
@@ -288,7 +289,7 @@ static void remove_junk(void)
289
static void remove_junk_on_signal(int signo)
290
{
291
remove_junk();
291
- signal(SIGINT, SIG_DFL);
292
+ sigchain_pop(signo);
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raise(signo);
294
}
295
@@ -438,7 +439,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
439
}
440
junk_git_dir = git_dir;
441
atexit(remove_junk);
441
- signal(SIGINT, remove_junk_on_signal);
442
+ sigchain_push(SIGINT, remove_junk_on_signal);
443
444
setenv(CONFIG_ENVIRONMENT, xstrdup(mkpath("%s/config", git_dir)), 1);
445
builtin-fetch--tool.c
+3
-2
@@ -2,6 +2,7 @@
2
#include "cache.h"
3
#include "refs.h"
4
#include "commit.h"
5
+#include "sigchain.h"
6
7
static char *get_stdin(void)
8
{
@@ -186,7 +187,7 @@ static void remove_keep(void)
187
static void remove_keep_on_signal(int signo)
188
{
189
remove_keep();
189
- signal(SIGINT, SIG_DFL);
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+ sigchain_pop(signo);
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raise(signo);
192
}
193
@@ -245,7 +246,7 @@ static int fetch_native_store(FILE *fp,
246
char buffer[1024];
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int err = 0;
248
248
- signal(SIGINT, remove_keep_on_signal);
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+ sigchain_push(SIGINT, remove_keep_on_signal);
250
atexit(remove_keep);
251
252
while (fgets(buffer, sizeof(buffer), stdin)) {
builtin-fetch.c
+3
-2
@@ -10,6 +10,7 @@
10
#include "transport.h"
11
#include "run-command.h"
12
#include "parse-options.h"
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+#include "sigchain.h"
14
15
static const char * const builtin_fetch_usage[] = {
16
"git fetch [options] [<repository> <refspec>...]",
@@ -58,7 +59,7 @@ static void unlock_pack(void)
59
static void unlock_pack_on_signal(int signo)
60
{
61
unlock_pack();
61
- signal(SIGINT, SIG_DFL);
62
+ sigchain_pop(signo);
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raise(signo);
64
}
65
@@ -672,7 +673,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
673
ref_nr = j;
674
}
675
675
- signal(SIGINT, unlock_pack_on_signal);
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+ sigchain_push(SIGINT, unlock_pack_on_signal);
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atexit(unlock_pack);
678
exit_code = do_fetch(transport,
679
parse_fetch_refspec(ref_nr, refs), ref_nr);
diff.c
+3
-2
@@ -12,6 +12,7 @@
12
#include "run-command.h"
13
#include "utf8.h"
14
#include "userdiff.h"
15
+#include "sigchain.h"
16
17
#ifdef NO_FAST_WORKING_DIRECTORY
18
#define FAST_WORKING_DIRECTORY 0
@@ -188,7 +189,7 @@ static void remove_tempfile(void)
189
static void remove_tempfile_on_signal(int signo)
190
{
191
remove_tempfile();
191
- signal(SIGINT, SIG_DFL);
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+ sigchain_pop(signo);
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raise(signo);
194
}
195
@@ -1902,7 +1903,7 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
1903
1904
if (!remove_tempfile_installed) {
1905
atexit(remove_tempfile);
1905
- signal(SIGINT, remove_tempfile_on_signal);
1906
+ sigchain_push(SIGINT, remove_tempfile_on_signal);
1907
remove_tempfile_installed = 1;
1908
}
1909
http-push.c
+6
-5
@@ -10,6 +10,7 @@
10
#include "exec_cmd.h"
11
#include "remote.h"
12
#include "list-objects.h"
13
+#include "sigchain.h"
14
15
#include <expat.h>
16
@@ -1363,7 +1364,7 @@ static void remove_locks(void)
1364
static void remove_locks_on_signal(int signo)
1365
{
1366
remove_locks();
1366
- signal(signo, SIG_DFL);
1367
+ sigchain_pop(signo);
1368
raise(signo);
1369
}
1370
@@ -2261,10 +2262,10 @@ int main(int argc, char **argv)
2262
goto cleanup;
2263
}
2264
2264
- signal(SIGINT, remove_locks_on_signal);
2265
- signal(SIGHUP, remove_locks_on_signal);
2266
- signal(SIGQUIT, remove_locks_on_signal);
2267
- signal(SIGTERM, remove_locks_on_signal);
2265
+ sigchain_push(SIGINT, remove_locks_on_signal);
2266
+ sigchain_push(SIGHUP, remove_locks_on_signal);
2267
+ sigchain_push(SIGQUIT, remove_locks_on_signal);
2268
+ sigchain_push(SIGTERM, remove_locks_on_signal);
2269
2270
/* Check whether the remote has server info files */
2271
remote->can_update_info_refs = 0;
lockfile.c
+7
-6
@@ -2,6 +2,7 @@
2
* Copyright (c) 2005, Junio C Hamano
3
*/
4
#include "cache.h"
5
+#include "sigchain.h"
6
7
static struct lock_file *lock_file_list;
8
static const char *alternate_index_output;
@@ -24,7 +25,7 @@ static void remove_lock_file(void)
25
static void remove_lock_file_on_signal(int signo)
26
{
27
remove_lock_file();
27
- signal(signo, SIG_DFL);
28
+ sigchain_pop(signo);
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raise(signo);
30
}
31
@@ -136,11 +137,11 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
137
lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
138
if (0 <= lk->fd) {
139
if (!lock_file_list) {
139
- signal(SIGINT, remove_lock_file_on_signal);
140
- signal(SIGHUP, remove_lock_file_on_signal);
141
- signal(SIGTERM, remove_lock_file_on_signal);
142
- signal(SIGQUIT, remove_lock_file_on_signal);
143
- signal(SIGPIPE, remove_lock_file_on_signal);
140
+ sigchain_push(SIGINT, remove_lock_file_on_signal);
141
+ sigchain_push(SIGHUP, remove_lock_file_on_signal);
142
+ sigchain_push(SIGTERM, remove_lock_file_on_signal);
143
+ sigchain_push(SIGQUIT, remove_lock_file_on_signal);
144
+ sigchain_push(SIGPIPE, remove_lock_file_on_signal);
145
atexit(remove_lock_file);
146
}
147
lk->owner = getpid();
sigchain.c
new
+43
@@ -0,0 +1,43 @@
1
+#include "sigchain.h"
2
+#include "cache.h"
3
+
4
+#define SIGCHAIN_MAX_SIGNALS 32
5
+
6
+struct sigchain_signal {
7
+ sigchain_fun *old;
8
+ int n;
9
+ int alloc;
10
+};
11
+static struct sigchain_signal signals[SIGCHAIN_MAX_SIGNALS];
12
+
13
+static void check_signum(int sig)
14
+{
15
+ if (sig < 1 || sig >= SIGCHAIN_MAX_SIGNALS)
16
+ die("BUG: signal out of range: %d", sig);
17
+}
18
+
19
+int sigchain_push(int sig, sigchain_fun f)
20
+{
21
+ struct sigchain_signal *s = signals + sig;
22
+ check_signum(sig);
23
+
24
+ ALLOC_GROW(s->old, s->n + 1, s->alloc);
25
+ s->old[s->n] = signal(sig, f);
26
+ if (s->old[s->n] == SIG_ERR)
27
+ return -1;
28
+ s->n++;
29
+ return 0;
30
+}
31
+
32
+int sigchain_pop(int sig)
33
+{
34
+ struct sigchain_signal *s = signals + sig;
35
+ check_signum(sig);
36
+ if (s->n < 1)
37
+ return 0;
38
+
39
+ if (signal(sig, s->old[s->n - 1]) == SIG_ERR)
40
+ return -1;
41
+ s->n--;
42
+ return 0;
43
+}
sigchain.h
new
+9
@@ -0,0 +1,9 @@
1
+#ifndef SIGCHAIN_H
2
+#define SIGCHAIN_H
3
+
4
+typedef void (*sigchain_fun)(int);
5
+
6
+int sigchain_push(int sig, sigchain_fun f);
7
+int sigchain_pop(int sig);
8
+
9
+#endif /* SIGCHAIN_H */
t/t0005-signals.sh
new
+22
@@ -0,0 +1,22 @@
1
+#!/bin/sh
2
+
3
+test_description='signals work as we expect'
4
+. ./test-lib.sh
5
+
6
+cat >expect <<EOF
7
+three
8
+two
9
+one
10
+EOF
11
+
12
+test_expect_success 'sigchain works' '
13
+ test-sigchain >actual
14
+ case "$?" in
15
+ 130) true ;; # POSIX w/ SIGINT=2
16
+ 3) true ;; # Windows
17
+ *) false ;;
18
+ esac &&
19
+ test_cmp expect actual
20
+'
21
+
22
+test_done
test-sigchain.c
new
+22
@@ -0,0 +1,22 @@
1
+#include "sigchain.h"
2
+#include "cache.h"
3
+
4
+#define X(f) \
5
+static void f(int sig) { \
6
+ puts(#f); \
7
+ fflush(stdout); \
8
+ sigchain_pop(sig); \
9
+ raise(sig); \
10
+}
11
+X(one)
12
+X(two)
13
+X(three)
14
+#undef X
15
+
16
+int main(int argc, char **argv) {
17
+ sigchain_push(SIGINT, one);
18
+ sigchain_push(SIGINT, two);
19
+ sigchain_push(SIGINT, three);
20
+ raise(SIGINT);
21
+ return 0;
22
+}