A question about file lock

[Xue Fuqiao]

Hi list,

I have a question regarding file locks.  In (info "(elisp) File Locks"):

 -- Function: unlock-buffer
[...]
     If the buffer is not modified, then the file should not be locked,
     so this function does nothing.

What if Emacs or the operating system crashes?  Will the lock files
disappear?  If not, after the crash, does this function work?

--
Best regards, Xue Fuqiao.