Split part of the Task struct into a separate struct InCall

The idea is that this leaves Tasks and OSThread in one-to-one
correspondence.  The part of a Task that represents a call into
Haskell from C is split into a separate struct InCall, pointed to by
the Task and the TSO bound to it.  A given OSThread/Task thus always
uses the same mutex and condition variable, rather than getting a new
one for each callback.  Conceptually it is simpler, although there are
more types and indirections in a few places now.

This improves callback performance by removing some of the locks that
we had to take when making in-calls.  Now we also keep the current Task
in a thread-local variable if supported by the OS and gcc (currently
only Linux).

1 files changed, 2 insertions, 2 deletions

diff --git a/rts/Threads.c b/rts/Threads.c
index 4f9560c36c..08b7aab66e 100644
--- a/rts/Threads.c
+++ b/rts/Threads.c
@@ -230,8 +230,8 @@ unblockOne_ (Capability *cap, StgTSO *tso,
       // We are waking up this thread on the current Capability, which
       // might involve migrating it from the Capability it was last on.
       if (tso->bound) {
-	  ASSERT(tso->bound->cap == tso->cap);
-	  tso->bound->cap = cap;
+	  ASSERT(tso->bound->task->cap == tso->cap);
+	  tso->bound->task->cap = cap;
       }
 
       tso->cap = cap;