Avoid infinite loops in caching layer

[ps-cgit] / cache.c

diff --git a/cache.c b/cache.c
index b034c480e0d9866de93bfa3866abda0cb0bd7df5..2e1ef8cc9e0fe7742965a1b3e845f12fa1fab13f 100644 (file)
--- a/cache.c
+++ b/cache.c
@@ -10,7 +10,7 @@
 
 const int NOLOCK = -1;
 
-int cache_lookup(struct cacheitem *item)
+void cache_prepare(struct cacheitem *item)
 {
        if (!cgit_query_repo) {
                item->name = xstrdup(fmt("%s/index.html", cgit_cache_root));
@@ -30,6 +30,10 @@ int cache_lookup(struct cacheitem *item)
                else
                        item->ttl = cgit_cache_repo_ttl;
        }
+}
+
+int cache_exist(struct cacheitem *item)
+{
        if (stat(item->name, &item->st)) {
                item->st.st_mtime = 0;
                return 0;
@@ -57,26 +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);
 }