From 318d106300102c19d114a4ea89265b0a4060d9cb Mon Sep 17 00:00:00 2001 From: Lars Hjemli Date: Mon, 11 Dec 2006 12:10:12 +0100 Subject: 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 --- cache.c | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-) (limited to 'cache.c') 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); } -- cgit v1.2.1