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>
Lars Hjemli hjemli@gmail.com
Mon, 11 Dec 2006 12:10:12 +0100
M
cache.c
→
cache.c
@@ -61,26 +61,35 @@ }
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); }
M
cgit.c
→
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_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))