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authorLars Hjemli <hjemli@gmail.com>2006-12-11 12:10:12 +0100
committerLars Hjemli <hjemli@gmail.com>2006-12-11 12:10:12 +0100
commit318d106300102c19d114a4ea89265b0a4060d9cb (patch)
tree3752575abec74ee0a2b544e36e3cc8f9cdfa1e66 /cache.c
parenta581ed8d6c15b0734b082fbadf0a907c2b170423 (diff)
Avoid infinite loops in caching layer
Add a global variable, cgit_max_lock_attemps, to avoid the possibility of
infinite loops when failing to acquire a lockfile. This could happen on
broken setups or under crazy server load.

Incidentally, this also fixes a lurking bug in cache_lock() where an
uninitialized returnvalue was used.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Diffstat (limited to 'cache.c')
-rw-r--r--cache.c35
1 files changed, 22 insertions, 13 deletions
diff --git a/cache.c b/cache.c
index 0ffa502..2e1ef8c 100644
--- a/cache.c
+++ b/cache.c
@@ -61,26 +61,35 @@ int cache_create_dirs()
 	return 1;
 }
 
+int cache_refill_overdue(const char *lockfile)
+{
+	struct stat st;
+
+	if (stat(lockfile, &st))
+		return 0;
+	else
+		return (time(NULL) - st.st_mtime > cgit_cache_max_create_time);
+}
+
 int cache_lock(struct cacheitem *item)
 {
-	int ret;
+	int i = 0;
 	char *lockfile = fmt("%s.lock", item->name);
 
- top:  
-       	item->fd = open(lockfile, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR|S_IWUSR);
+ top:
+	if (++i > cgit_max_lock_attempts)
+		die("cache_lock: unable to lock %s: %s",
+		    item->name, strerror(errno));
+
+       	item->fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR);
+
 	if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs())
 		goto top;
-	if (item->fd == NOLOCK && errno == EEXIST) {
-		struct stat st;
-		time_t t;
-		if (stat(lockfile, &st))
-			return ret;
-		t = time(NULL);
-		if (t-st.st_mtime > cgit_cache_max_create_time && 
-		    !unlink(lockfile))
+
+	if (item->fd == NOLOCK && errno == EEXIST &&
+	    cache_refill_overdue(lockfile) && !unlink(lockfile))
 			goto top;
-		return 0;
-	}
+
 	return (item->fd > 0);
 }