#4493: Child from forkProcess calls select/read on parent's Handle, stealing
data
from parent
-------------------------------+--------------------------------------------
Reporter: josh | Owner:
Type: bug | Status: infoneeded
Priority: high | Milestone: 7.0.2
Component: Runtime System | Version: 6.12.1
Keywords: | Testcase: yes
Blockedby: | Difficulty:
Os: Linux | Blocking:
Architecture: x86_64 (amd64) | Failure: Incorrect result at runtime
-------------------------------+--------------------------------------------
Comment(by joeyhess):
Josh may have a better test case, but it can be reproduced by the
following.
{{{
import System.Cmd.Utils
main = do
(h, stream) <- pipeFrom "find" ["."]
mapM (\file -> pipeFrom "ls" ["-l", file]) $ lines stream
}}}
This code is intentionally itself bad, and will leak FDs a lot, but if
you run it in a directory with lots of contents, you'll see that
sometimes, before dying due to too many open FDs, it runs `ls` with a
parameter that is not a complete line output by `find`, due to the data
stealing problem.
Here I run it in ghc's own source tree:
{{{
j...@wren:~/tmp/ghc6-6.12.1>runghc ~/testcase.hs
ls: cannot access ./.pc/alpha-tcforeign/systemTests/A/c_src/hello.c: No
such
file or directory
ls: cannot access ./libraries/Cabal/tests/ow: No such file or directory
repo.hs: createPipe: resource exhausted (Too many open files)
j...@wren:~/tmp/ghc6-6.12.1>find |grep libraries/Cabal/tests/ow
j...@wren:~/tmp/ghc6-6.12.1>
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4493#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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