[Haskell-cafe] Why don't my OS threads terminate?

Bas van Dijk v.dijk.bas at gmail.com
Thu Mar 10 19:20:28 CET 2011

On 10 March 2011 18:11, Simon Marlow <marlowsd at gmail.com> wrote:
> On 28/02/11 15:59, Bas van Dijk wrote:
>> On 25 February 2011 19:10, Bas van Dijk<v.dijk.bas at gmail.com>  wrote:
>>> On 25 February 2011 18:27, sclv<s.clover at gmail.com>  wrote:
>>>> Bas van Dijk-2 wrote:
>>>>> I believe the OS threads are created by my levmar library. This
>>>>> library uses bindings-levmar[4] which is a binding to a C library.
>>>>> bindings-levmar uses safe FFI calls because the levmar C procedures
>>>>> are reentrant (they need to call back into Haskell to execute the
>>>>> model function). I believe the RTS creates an OS thread for each safe
>>>>> FFI call.
>>>> Sounds like #4262: http://hackage.haskell.org/trac/ghc/ticket/4262
>>>> (Should be fixed in head)
>>> That looks exactly like my problem. I will try it out with ghc head on
>>> monday.
>> In ghc-HEAD (7.1.20110227) the bug is fixed, great!
>> The bug still appears in ghc-7.0.2-rc2, so I assume the patch in #4262
>> was not merged in that release.
>> Will it be merged into the upcoming ghc-7.0.2?
> I'm slightly worried by this.  #4262 was not an OS thread "leak", but rather
> that when the program needs fewer OS threads we weren't returning the
> surplus OS threads back to the system.  #4262 doesn't make programs use an
> ever-increasing number of OS threads.  It's an optimisation rather than a
> bug, which is why we didn't merge the patch into the 7.0 branch.
> So I'm concerned because the symptom you describe sounds more like a leak.
> #4850 could have caused it, but the fix for that was merged into 7.0.2.

My bug is solved in 7.0.2.



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