[commit: ghc] ghc-lwc2: Removing checks from setSContCapability. Races in stg_atomicSwitch causes SCont stealing to fail. (9bfbcf8)

[Sivaramakrishnan Krishnamoorthy Chandrasekaran]

Repository : http://darcs.haskell.org/ghc.git/

On branch  : ghc-lwc2

https://github.com/ghc/ghc/commit/9bfbcf81e797c316dcd61f43f1a2e45be9bf6067

>---------------------------------------------------------------

commit 9bfbcf81e797c316dcd61f43f1a2e45be9bf6067
Author: KC Sivaramakrishnan <chandras at cs.purdue.edu>
Date:   Sun May 5 23:41:08 2013 -0400

    Removing checks from setSContCapability. Races in stg_atomicSwitch causes SCont stealing to fail.

>---------------------------------------------------------------

 libraries/base/LwConc/Substrate.hs               | 8 ++------
 rts/Threads.c                                    | 1 -
 tests/Benchmarks/Sieve/ConcurrentListStealing.hs | 2 +-
 tests/Benchmarks/Sieve/Makefile                  | 2 +-
 4 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/libraries/base/LwConc/Substrate.hs b/libraries/base/LwConc/Substrate.hs
index 7b1d608..afa5c57 100644
--- a/libraries/base/LwConc/Substrate.hs
+++ b/libraries/base/LwConc/Substrate.hs
@@ -648,16 +648,12 @@ getSContCapabilityIO (SCont sc) = IO $
   \s -> case getSContCapability# sc s of
              (# s, n #) -> (# s, I# n #)
 
-
--- We must own the capability (i.e, scont->cap == MyCapability ()). Otherwise,
--- will throw a runtime error.
+-- Updates tso->cap to given cap
 setSContCapability :: SCont -> Int -> IO ()
 setSContCapability (SCont sc) (I# i) = do
   cc <- getCurrentCapabilityIO
   scc <- getSContCapabilityIO $ SCont sc
-  if cc == scc
-    then IO $ \s -> case setSContCapability# sc i s of s -> (# s, () #)
-    else error "setSContCapability: SCont must belong to the current capability"
+  IO $ \s -> case setSContCapability# sc i s of s -> (# s, () #)
 
 sleepCapability :: PTM a
 sleepCapability = PTM $ \s -> sleepCapability# s
diff --git a/rts/Threads.c b/rts/Threads.c
index 9155cda..63ca915 100644
--- a/rts/Threads.c
+++ b/rts/Threads.c
@@ -248,7 +248,6 @@ setOwningCapability (Capability *cap USED_IF_DEBUG,
                      nat target) {
   debugTrace (DEBUG_sched, "cap %d: Setting the capability of thread %d to %d",
               cap->no, tso->id, target);
-  ASSERT (cap == tso->cap);
   ASSERT (target < enabled_capabilities);
   tso->cap = &capabilities[target];
 }
diff --git a/tests/Benchmarks/Sieve/ConcurrentListStealing.hs b/tests/Benchmarks/Sieve/ConcurrentListStealing.hs
index c5d84f2..fb2cfcb 100644
--- a/tests/Benchmarks/Sieve/ConcurrentListStealing.hs
+++ b/tests/Benchmarks/Sieve/ConcurrentListStealing.hs
@@ -15,7 +15,7 @@
 -----------------------------------------------------------------------------
 
 
-module ConcurrentList
+module ConcurrentListStealing
 (
   Sched
 , SCont
diff --git a/tests/Benchmarks/Sieve/Makefile b/tests/Benchmarks/Sieve/Makefile
index 96e57da..ac8d646 100644
--- a/tests/Benchmarks/Sieve/Makefile
+++ b/tests/Benchmarks/Sieve/Makefile
@@ -3,7 +3,7 @@ TARGET := sieve-vanilla.bin sieve-lwc.bin sieve-TMVar.bin sieve-vanilla-TMVar.bi
 include ../../config.mk
 
 TOP := ../../../
-GHC_OPTS_EXTRA=-O2 -threaded -XBangPatterns -XCPP -XGeneralizedNewtypeDeriving -funbox-strict-fields -optc-O3 -debug
+GHC_OPTS_EXTRA=-threaded -XBangPatterns -XCPP -XGeneralizedNewtypeDeriving -funbox-strict-fields -O2 -optc-O3 -debug
 
 PROFILE_FLAGS := -DPROFILE_ENABLED -prof -auto-all -fprof-auto