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>

1 file changed, 8 insertions, 1 deletion

diff --git a/cgit.c b/cgit.c
index 7f14016..dc91125 100644
--- a/cgit.c
+++ b/cgit.c
@@ -31,6 +31,7 @@ char *cgit_virtual_root = NULL;
 
 char *cgit_cache_root   = "/var/cache/cgit";
 
+int cgit_max_lock_attempts     =  5;
 int cgit_cache_root_ttl        =  5;
 int cgit_cache_repo_ttl        =  5;
 int cgit_cache_dynamic_ttl     =  5;
@@ -465,11 +466,17 @@ static void cgit_fill_cache(struct cacheitem *item)
 
 static void cgit_refresh_cache(struct cacheitem *item)
 {
+	int i = 0;
+
 	cache_prepare(item);
  top:
+	if (++i > cgit_max_lock_attempts) {
+		die("cgit_refresh_cache: unable to lock %s: %s",
+		    item->name, strerror(errno));
+	}
 	if (!cache_exist(item)) {
 		if (!cache_lock(item)) {
-			sched_yield();
+			sleep(1);
 			goto top;
 		}
 		if (!cache_exist(item))