masaori335 commented on code in PR #12601:
URL: https://github.com/apache/trafficserver/pull/12601#discussion_r2453602137
##########
src/iocore/cache/Cache.cc:
##########
@@ -342,7 +342,9 @@ Cache::open_read(Continuation *cont, const CacheKey *key,
CacheFragType type, st
CacheVC *c = nullptr;
{
CACHE_TRY_LOCK(lock, stripe->mutex, mutex->thread_holding);
- if (!lock.is_locked() || (od = stripe->open_read(key)) ||
stripe->directory.probe(key, stripe, &result, &last_collision)) {
+ CACHE_DIR_TRY_LOCK_SHARED(dir_lock, stripe->dir_mutex);
+ if (!lock.is_locked() || !dir_lock.is_locked() || (od =
stripe->open_read(key)) ||
+ stripe->directory.probe(key, stripe, &result, &last_collision)) {
Review Comment:
Having `mutex` and `dir_mutex` might be good approach. When we call
`Directory::probe` with read lock of `dir_mutex`, but it needs write operation
(it's rare case I assume), we can wait for `mutex` lock. Obviously, we have to
be careful for dead lock.
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