[GHC] #3316: Deadlock in non-threaded RTS with hPutBuf

[GHC]

#3316: Deadlock in non-threaded RTS with hPutBuf
-------------------+--------------------------------------------------------
Reporter:  ganesh  |          Owner:          
    Type:  bug     |         Status:  new     
Priority:  normal  |      Component:  Compiler
 Version:  6.8.3   |       Severity:  normal  
Keywords:          |       Testcase:          
      Os:  Linux   |   Architecture:  x86     
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 Using the non-threaded RTS, the attached program works fine in 6.8.2, but
 deadlocks in 6.8.3 and later GHCs (including 6.10.3 and 6.11.20090618).

 The program forks (runInteractiveProcess) two copies of cat, then forks
 off two  separate threads (forkIO) to write a large buffer to stdin of
 each copy, and also lazily reads the outputs of each copy of cat, forcing
 the results with an equality test.

 From strace, it looks like 6.8.2 is correctly selecting on multiple FDs at
 once (though just 3, rather than all 4, which I don't understand), whereas
 6.8.3 doesn't and hence ends up in a deadlock when the pipe it wants to
 use blocks while some other pipe is actually ready.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3316>
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