ignore long locked inactive cache entry 官方回复了
The "ignore long locked inactive cache entry" alert indicates that nginx was trying to remove a cache entry, but failed to do this because the entry was locked. This may be either result of a bug, or may happen if a worker process is killed or crashed.
That is, this may happen, e.g., if your server run out of memory at some point and OOM-killer killed an nginx worker process.
To find out what actually happened you may want to investigate error log before the first "ignore long locked" alert.