[GHC] #14725: memory leak: forkOS not releasing thread local `Task` struct upon end of thread

[GHC]

#14725: memory leak: forkOS not releasing thread local `Task` struct upon end of
thread
-------------------------------------+-------------------------------------
        Reporter:  RobertZabel       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Runtime System    |              Version:  8.2.2
      Resolution:                    |             Keywords:  forkOS memory
                                     |  leak
Operating System:  POSIX             |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by RobertZabel:

Old description:

> I came to notice a memory leak in the runtime system while letting warp
> use `forkOS` and conducting a load test.\\
>  A minimal snippet to reproduce:
>
> {{{#!hs
> module Main where
> import Control.Concurrent
>
> main :: IO ()
> main = replicateM_ 10000000 $ forkOS $ return ()
> }}}
>
> This patch will clean up the thread local `Task` struct just before
> threads  created by forkOS terminate.
>
> {{{
> diff --git a/rts/posix/OSThreads.c b/rts/posix/OSThreads.c
> index c9adf4e..bd4e75d 100644
> --- a/rts/posix/OSThreads.c
> +++ b/rts/posix/OSThreads.c
> @@ -223,6 +223,7 @@ forkOS_createThreadWrapper ( void * entry )
>      cap = rts_lock();
>      rts_evalStableIO(&cap, (HsStablePtr) entry, NULL);
>      rts_unlock(cap);
> +    rts_done();
>      return NULL;
>  }
> }}}
>
> I think win32 platforms need an equivalent patch, but unfortunately I
> cannot verify that. \\
> Hence I'm only targeting posix here.

New description:

 I came to notice a memory leak in the runtime system while letting warp
 use `forkOS` and conducting a load test.\\
  A minimal snippet to reproduce:

 {{{#!hs
 module Main where
 import Control.Concurrent
 import Control.Monad

 main :: IO ()
 main = replicateM_ 10000000 $ forkOS $ return ()
 }}}

 This patch will clean up the thread local `Task` struct just before
 threads  created by forkOS terminate.

 {{{
 diff --git a/rts/posix/OSThreads.c b/rts/posix/OSThreads.c
 index c9adf4e..bd4e75d 100644
 --- a/rts/posix/OSThreads.c
 +++ b/rts/posix/OSThreads.c
 @@ -223,6 +223,7 @@ forkOS_createThreadWrapper ( void * entry )
      cap = rts_lock();
      rts_evalStableIO(&cap, (HsStablePtr) entry, NULL);
      rts_unlock(cap);
 +    rts_done();
      return NULL;
  }
 }}}

 I think win32 platforms need an equivalent patch, but unfortunately I
 cannot verify that. \\
 Hence I'm only targeting posix here.

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14725#comment:1>
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