Re: [GHC] #2560: killThread and getChanContents appear to interact strangely
#2560: killThread and getChanContents appear to interact strangely -+-- Reporter: batterseapower|Owner: Type: bug | Status: closed Priority: normal|Milestone: 6.10.2 Component: Runtime System| Version: 6.9 Severity: normal| Resolution: invalid Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by simonmar): * status: new = closed * resolution: = invalid Comment: I've spent a long time staring at this ticket today, and I'm not convinced there's a bug. `modifyMVar` is exception-safe, and so is `getChanContents`, as far as I can tell. Ian's point is true, that you can't guarantee to keep exceptions blocked when calling a library function, but I don't think that makes anything unsafe in this case. Exception-safety is all about making sure that `MVars` get replaced if an exception is raised, and I think that always holds for `modifyMVar` and `getChanContents`. No, I suspect there's a bug in the program logic. It just loops when it gets to a chunk size of 1, and if you look at the definition of `readWithTimeout`, you can see why. If the chunk size is 1, it just recurses with the same value for `n`. At least, that's my guess - I don't fully understand what this program is trying to do. If you disagree, plesae re-open the bug. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2560#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2560: killThread and getChanContents appear to interact strangely
#2560: killThread and getChanContents appear to interact strangely
-+--
Reporter: batterseapower|Owner:
Type: bug | Status: new
Priority: normal|Milestone: 6.10.2
Component: Runtime System| Version: 6.9
Severity: normal| Resolution:
Keywords:| Difficulty: Unknown
Testcase:| Os: Unknown/Multiple
Architecture: Unknown/Multiple |
-+--
Comment (by igloo):
OK, I think the problem is that
{{{
readChan = modifyMVar ...
}}}
and
{{{
modifyMVar :: MVar a - (a - IO (a,b)) - IO b
modifyMVar m io =
block $ do
a - takeMVar m
(a',b) - unblock (io a) `onException` putMVar m a
putMVar m a'
return b
}}}
so although you are calling `readChan` with exceptions blocked, they are
being unblocked by the library.
I'm not sure what the best solution is.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2560#comment:3
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Re: [GHC] #2560: killThread and getChanContents appear to interact strangely
#2560: killThread and getChanContents appear to interact strangely --+- Reporter: batterseapower| Owner: Type: bug | Status: new Priority: normal| Milestone: 6.10.2 Component: Runtime System|Version: 6.9 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Architecture: Unknown/Multiple Os: Unknown/Multiple | --+- Changes (by igloo): * difficulty: = Unknown * os: MacOS X = Unknown/Multiple * architecture: x86 = Unknown/Multiple * milestone: = 6.10.2 Comment: I can reproduce this on amd64/Linux too, and with 6.8.2 as well as the HEAD. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2560#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2560: killThread and getChanContents appear to interact strangely
#2560: killThread and getChanContents appear to interact strangely ---+ Reporter: batterseapower |Owner: Type: bug | Status: new Priority: normal |Milestone: Component: Runtime System | Version: 6.9 Severity: normal | Resolution: Keywords: | Testcase: Architecture: x86 | Os: MacOS X ---+ Comment (by batterseapower): Forgot to mention: the test case above uses a 5000 element list. For some reason, this causes quite a few failures on my machine. If it doesn't work on yours, try bumping it up to 10 or so, which should make the failure certain. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2560#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
