Re: [Haskell-cafe] terminateProcess leaves zombie processes around
On Wed, Dec 7, 2011 at 20:35, Jason Dagit wrote: > > They *do* terminate; a zombie is a dead process waiting for its parent to > > reap it with waitForProcess. There's also some POSIX stuff you can do to > > have them auto-reaped, but doing that correctly and portably is somewhat > > painful. > > You can use a double fork to make this portable and not painful. It's > just that you have to fork twice, which can be expensive in some > cases. > And problematic if you're using a pipe to communicate with the child, which seemed quite possible. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
On Wed, Dec 7, 2011 at 7:19 AM, Brandon Allbery wrote: > On Wed, Dec 7, 2011 at 06:47, Dan Rosén wrote: >> >> I'm using Haskell to run a lot of instances of an Automated Thorem Prover, >> eprover. I have pasted a smaller version of my program at >> http://hpaste.org/54954. It runs eprover sequentially on all input files, >> with a timeout of 100ms. Unfortunately, it leaves a lot of zombie processes >> around, probably due to the fact that terminateProcess fails to terminate >> them, even though eprover terminates on SIGTERM. > > > They *do* terminate; a zombie is a dead process waiting for its parent to > reap it with waitForProcess. There's also some POSIX stuff you can do to > have them auto-reaped, but doing that correctly and portably is somewhat > painful. You can use a double fork to make this portable and not painful. It's just that you have to fork twice, which can be expensive in some cases. Explanation here: http://stackoverflow.com/a/881434/5113 Here is a Haskell example from xmonad: http://hackage.haskell.org/packages/archive/xmonad/0.7/doc/html/src/XMonad-Core.html#doubleFork If you're planning to send a SIGTERM later, then double forking may make that harder as I think you'd have to communicate the PID up one level. I hope that helps, Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
Thank you very much for your answers. Felipe's suggestion to use waitForProcess after terminateProcess did the trick. No more zombies around :) Best regards, Dan Rosén On Wed, Dec 7, 2011 at 4:39 PM, Donn Cave wrote: > Quoth Felipe Almeida Lessa , > > On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery > wrote: > >> They *do* terminate; a zombie is a dead process waiting for its parent > to > >> reap it with waitForProcess. There's also some POSIX stuff you can do > to > >> have them auto-reaped, but doing that correctly and portably is somewhat > >> painful. > > > > But zombie processes do consume a row in the process table, right? If > > so, then it's bad to have them around. > > Correct. As noted above, clean up with waitForProcess to release this > resource. If it's more convenient, that could be done up front, by > forking twice and waiting for the intermediate process. One possibly > convenient way to do that might be something like runCommand "eprover &". > >Donn > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
Quoth Felipe Almeida Lessa , > On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery wrote: >> They *do* terminate; a zombie is a dead process waiting for its parent to >> reap it with waitForProcess. There's also some POSIX stuff you can do to >> have them auto-reaped, but doing that correctly and portably is somewhat >> painful. > > But zombie processes do consume a row in the process table, right? If > so, then it's bad to have them around. Correct. As noted above, clean up with waitForProcess to release this resource. If it's more convenient, that could be done up front, by forking twice and waiting for the intermediate process. One possibly convenient way to do that might be something like runCommand "eprover &". Donn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
On Wed, Dec 7, 2011 at 10:27, Felipe Almeida Lessa wrote: > On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery > wrote: > > They *do* terminate; a zombie is a dead process waiting for its parent to > > reap it with waitForProcess. There's also some POSIX stuff you can do to > > have them auto-reaped, but doing that correctly and portably is somewhat > > painful. > > But zombie processes do consume a row in the process table, right? If > so, then it's bad to have them around. Yes, and they count against the per-uid process limit. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery wrote: > They *do* terminate; a zombie is a dead process waiting for its parent to > reap it with waitForProcess. There's also some POSIX stuff you can do to > have them auto-reaped, but doing that correctly and portably is somewhat > painful. But zombie processes do consume a row in the process table, right? If so, then it's bad to have them around. -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
On Wed, Dec 7, 2011 at 06:47, Dan Rosén wrote: > I'm using Haskell to run a lot of instances of an Automated Thorem Prover, > eprover. I have pasted a smaller version of my program at > http://hpaste.org/54954. It runs eprover sequentially on all input files, > with a timeout of 100ms. Unfortunately, it leaves a lot of zombie processes > around, probably due to the fact that terminateProcess fails to terminate > them, even though eprover terminates on SIGTERM. > They *do* terminate; a zombie is a dead process waiting for its parent to reap it with waitForProcess. There's also some POSIX stuff you can do to have them auto-reaped, but doing that correctly and portably is somewhat painful. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] terminateProcess leaves zombie processes around
Quick suggestion: did you try using waitForProcess just after terminateProcess? Cheers, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] terminateProcess leaves zombie processes around
Hi Haskell-Cafe, I'm using Haskell to run a lot of instances of an Automated Thorem Prover, eprover. I have pasted a smaller version of my program at http://hpaste.org/54954. It runs eprover sequentially on all input files, with a timeout of 100ms. Unfortunately, it leaves a lot of zombie processes around, probably due to the fact that terminateProcess fails to terminate them, even though eprover terminates on SIGTERM. I have tried to use System.Timeout.timeout around readProcess, but without surprise it did not work. Another way of doing it is to use the timeout from gnu-coreutils, but the timeout resolution is in seconds (same with eprover's flag --cpu-limit). Any ideas how I could write my code to get a clean termination of this process? Best, Dan Rosén ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
