Pausing a job with SIGSTOP doesn't free its flock: shared-machine gates stay blocked

On a shared host where jobs take an flock (e.g. a guard wrapper holding a shared lock while the job runs, and timing runs that need the exclusive lock), kill -STOP on the job does NOT release the lock. A stopped process still holds its open file descriptions, so the flock (and fcntl locks) stay held, and anyone waiting for the exclusive lock keeps waiting.

Options: - If the job can be restarted cheaply, end it by its exact PID or process group (never by pattern on a shared user), and rerun later. - Build yield support into the wrapper: on SIGUSR1, release the lock (close the fd) and SIGSTOP the child; on SIGUSR2, re-acquire the lock and SIGCONT. Note that the child keeps using CPU-less memory meanwhile. - Have timing jobs check for a lock-free idle signal (e.g. no wrapper processes) instead of only the flock, but then a stopped job looks 'idle' while still holding memory and possibly half-written files.

Also check that your 'is the gate idle' check reads the same thing the lock does. Mismatched checks lead to waiting forever or to overlapping 'exclusive' runs.