Subject: Re: [PATCH] gc: remove gc.pid file at end of execution

From: Jonathan Nieder <[email-masked]>
Date: Fri, 27 Sep 2013 17:33:20 -0700

Matthieu Moy wrote:

> This file isn't really harmful, but isn't useful either, and can create
> minor annoyance for the user:

Would something like the following make sense, to ensure the gc.pid file is
always removed on normal exit?

Signed-off-by: Jonathan Nieder <[email-masked]>

diff --git c/builtin/gc.c i/builtin/gc.c
index 6e0d81a..fbbc144 100644
--- c/builtin/gc.c
+++ i/builtin/gc.c
@@ -14,6 +14,7 @@
 #include "cache.h"
 #include "parse-options.h"
 #include "run-command.h"
+#include "sigchain.h"
 #include "argv-array.h"
 
 #define FAILED_RUN "failed to run %s"
@@ -167,6 +168,21 @@ static int need_to_gc(void)
 	return 1;
 }
 
+static char *pidfile;
+
+static void remove_pidfile(void)
+{
+	if (pidfile)
+		unlink(pidfile);
+}
+
+static void remove_pidfile_on_signal(int signo)
+{
+	remove_pidfile();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
 /* return NULL on success, else hostname running the gc */
 static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 {
@@ -179,13 +195,19 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	FILE *fp;
 	int fd, should_exit;
 
+	if (pidfile)
+		/* already locked */
+		return NULL;
+
 	if (gethostname(my_host, sizeof(my_host)))
 		strcpy(my_host, "unknown");
 
-	fd = hold_lock_file_for_update(&lock, git_path("gc.pid"),
+	pidfile = git_pathdup("gc.pid");
+
+	fd = hold_lock_file_for_update(&lock, pidfile,
 				       LOCK_DIE_ON_ERROR);
 	if (!force) {
-		fp = fopen(git_path("gc.pid"), "r");
+		fp = fopen(pidfile, "r");
 		memset(locking_host, 0, sizeof(locking_host));
 		should_exit =
 			fp != NULL &&
@@ -208,6 +230,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 		if (should_exit) {
 			if (fd >= 0)
 				rollback_lock_file(&lock);
+			pidfile = NULL;
 			*ret_pid = pid;
 			return locking_host;
 		}
@@ -219,6 +242,9 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	strbuf_release(&sb);
 	commit_lock_file(&lock);
 
+	sigchain_push_common(remove_pidfile_on_signal);
+	atexit(remove_pidfile);
+
 	return NULL;
 }