From fbaf1171b4e343929dd43ecac7cd9d1c692b84ec Mon Sep 17 00:00:00 2001 From: Lars Hjemli <hjemli@gmail.com> Date: Mon, 11 Dec 2006 22:53:50 +0100 Subject: Don't truncate valid cachefiles An embarrassing thinko in cgit_check_cache() would truncate valid cachefiles in the following situation: 1) process A notices a missing/expired cachefile 2) process B gets scheduled, locks, fills and unlocks the cachefile 3) process A gets scheduled, locks the cachefile, notices that the cachefile now exist/is not expired anymore, and continues to overwrite it with an empty lockfile. Thanks to Linus for noticing (again). Signed-off-by: Lars Hjemli <hjemli@gmail.com> --- cache.c | 5 +++++ cgit.c | 14 ++++++++++---- cgit.h | 1 + 3 files changed, 16 insertions(+), 4 deletions(-) diff --git a/cache.c b/cache.c index 2e1ef8c..b947a34 100644 --- a/cache.c +++ b/cache.c @@ -99,6 +99,11 @@ int cache_unlock(struct cacheitem *item) return (rename(fmt("%s.lock", item->name), item->name) == 0); } +int cache_cancel_lock(struct cacheitem *item) +{ + return (unlink(fmt("%s.lock", item->name)) == 0); +} + int cache_expired(struct cacheitem *item) { if (item->ttl < 0) diff --git a/cgit.c b/cgit.c index d1abaa0..0f72f2d 100644 --- a/cgit.c +++ b/cgit.c @@ -61,13 +61,19 @@ static void cgit_check_cache(struct cacheitem *item) sleep(1); goto top; } - if (!cache_exist(item)) + if (!cache_exist(item)) { cgit_fill_cache(item); - cache_unlock(item); + cache_unlock(item); + } else { + cache_cancel_lock(item); + } } else if (cache_expired(item) && cache_lock(item)) { - if (cache_expired(item)) + if (cache_expired(item)) { cgit_fill_cache(item); - cache_unlock(item); + cache_unlock(item); + } else { + cache_cancel_lock(item); + } } } diff --git a/cgit.h b/cgit.h index c1dcc97..c9554a7 100644 --- a/cgit.h +++ b/cgit.h @@ -66,6 +66,7 @@ extern int cgit_parse_query(char *txt, configfn fn); extern void cache_prepare(struct cacheitem *item); extern int cache_lock(struct cacheitem *item); extern int cache_unlock(struct cacheitem *item); +extern int cache_cancel_lock(struct cacheitem *item); extern int cache_exist(struct cacheitem *item); extern int cache_expired(struct cacheitem *item); -- cgit v1.2.3