[GHC] #10345: Testsuite timeout_multiplier setting does not work as expected

[GHC]

#10345: Testsuite timeout_multiplier setting does not work as expected
-------------------------------------+-------------------------------------
        Reporter:  jstolarek         |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Test Suite        |              Version:  7.11
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D982
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by thomie):

 Replying to [comment:1 thomie]:
 > The issue only I seem to be having is that running `python
 testsuite/timeout/timeout.py 10 'echo ok' ` doesn't return immediately,
 but only after 10 seconds.

 I finally figured this one out. I had `stty tostop` set in `~/.bashrc`.
 When `stty tostop` is set, a background process that tries to write to the
 terminal receives a SIGTTOU signal, which suspends it.

 In timeout.py, the first thing the child process does is call
 `os.setpgrp()`. This creates a new process group, with the child process
 itself as process group leader. Because only one process group per session
 can be the foreground process group, it will be a background process
 group.

 I'm not sure yet //why// timeout.py turns the child process that it
 creates into a background process. One implication is that `CTRL-C`
 doesn't kill it.

 References:
 * https://www.win.tue.nl/~aeb/linux/lk/lk-10.html
 * http://www.linusakesson.net/programming/tty/index.php

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10345#comment:12>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler