On 30 August 2013 06:01, Glenn Fowler <[email protected]> wrote: > > On Fri, 30 Aug 2013 04:04:34 +0200 Cedric Blancher wrote: >> On 22 August 2013 00:35, Irek Szczesniak <[email protected]> wrote: >> > On Wed, Aug 21, 2013 at 4:09 PM, David Korn <[email protected]> wrote: >> >> cc: [email protected] >> >> Subject: Re: Re: [ast-developers] [patch] kill(1) |sigqueue()| >> >> fixes+|EAGAIN| handling etc. ... / was: Re: |sigqueue()| fixes+|EAGAIN| >> >> handling etc. ... >> >> -------- >> >> 2. Add -R to handle EAGAIN >> >> I don't think that this is needed. EAGAIN should be handled >> >> as it is with fork with an exponential back-off algorithm that >> >> times out after around 30 seconds. EINTR will cause a retry >> >> unless trapnote has pending trap or signal to process in which >> >> case kill will fail. >> > >> > I think I know why Roland added this option: >> > 1. If the target process or thread is stopped it cannot consume >> > signals. They just queue up. If the queue is full an attempt to >> > sigqueue() one returns with EAGAIN and you have a variation of the >> > Livelock [http://en.wikipedia.org/wiki/Deadlock#Livelock]. You can try >> > to experiment with that by using ulimit -i 5. >> > 2. Spinning with EAGAIN may not always be desirable for a realtime >> > application. Realtime != fast, it must be able to guarantee to act in >> > a determinable amount of time. The default case should be to spin with >> > EAGAIN (after all, ksh93 is a high level language), but give the >> > programmer the ability to do the EGAIN loop themselves. That's what we >> > did until Roland invented the -R option. > >> That was the reason. So -C has a use and -R has a rightful use, too > >> but the discussion is moot as the patch wasn't taken for >> ast-ksh.2013-08-29. So again a shell where kill -q doesn't work in a >> production environment. Which drives me seriously crazy. >> I start to understand the rise of perl (which ksh93 could've easily >> crushed): they just take patches in time while ksh93 delays them over >> and over and over again > > some patch proposals require thought before making it into a release > discussion is part of that process
But it has been discussed and went through many discussions before Roland send it to the list. There has been a lot of thought behind that patch, more than I liked. Ced -- Cedric Blancher <[email protected]> Institute Pasteur _______________________________________________ ast-developers mailing list [email protected] http://lists.research.att.com/mailman/listinfo/ast-developers
