title: How to display the process currently holding a semaphore?
body: <p>In userspace Linux, I have a process blocking on a semaphore, as found by strace. Once the error condition occurs, the blocking is repeatable, so there must be another process that holds the semaphore and did not release it.</p>
  
  <p>Is there a way to know which other process is currently holding the semaphore?</p>
  
  <p><code>ipcs</code> lists the semaphore, so does /proc/sysvipc/sem. Where can I find info on the holding process?</p>