Closing the window of a printing program left the pipe full, and the flushes
on the way out blocked on a compiler thread that was busy answering the very
request asking to run it again. program_state still said RUNNING, so rerun
refused a finished program as "the program is already running".
Two flushes moved. flan_exit no longer flushes before the hook -- exit(3)
flushes for itself, so that call only ever ran on the merged path, and there
it was the first thing to block. flan_merged_park flips the state under the
lock first and flushes after, because a state flip is two stores and cannot
wait on anything.
What widens is the window in which the program is parked and not yet on the
condvar. Nothing is lost there: program_asked is the fact and a signal
delivered to nobody is discarded. Two re-runs in that window are both
answered ok for one run, which is the trade against a refusal that was false.
Joseph Ferano
c1ccc318f7