blocking waitpid based event-loop

blocking waitpid based event-loop

[Andrew Cagney]

Hi,

The new core event-loop, that is implemented using a blocking waitpid 
call (and not dependent on SIGCHLD), has been fully committed  The old 
SIGCHLD + WAITPID/NOHANG based event loop had a race where, after a 
SIGCHLD, it could call WAITPID/NOHANG before the kernel had made the 
corresponding WAITPID event ready; this leading to frysk hanging as it 
didn't appear to receive the event.

Not that it is still disabled though.  While the FC-5 test results are 
identical to the old event-loop, it's managing to generate some 
mysterious "unknown pid" messages - perhaps it is working a little too 
well :-)

If you want to try the the new event loop, make an obvious tweak to 
frysk.proc.Manager.usePoll.  I'll look at the possibility of adding an 
--event-loop={poll,wait} option.

Next will be merging the ptrace-thread into the event-loop thread 
allowing for much of that thread's overhead to be eliminated.  After 
that Phil and I will see about making frysk use bulk ptrace transfers.

Andrew