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

26 Jan 2018

      #14725: memory leak: forkOS not releasing thread local `Task` struct upon end of
thread
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           Reporter:  RobertZabel         |             Owner:  (none)
               Type:  bug                 |            Status:  new
           Priority:  normal              |         Milestone:
          Component:  Runtime System      |           Version:  8.2.2
           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:
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 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.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14725
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