When using rts_setInCallCapability, lock incall threads

This diff makes sure that incall threads, when using `rts_setInCallCapability`, will be created as locked.
If the thread is not locked, the thread might end up being scheduled to a different capability.
While this is mentioned in the docs for `rts_setInCallCapability,`, it makes the method significantly less useful as there is no guarantees on the capability being used.

This commit also adds a test to make sure things stay on the correct capability.

1 files changed, 4 insertions, 4 deletions

diff --git a/includes/RtsAPI.h b/includes/RtsAPI.h
index 3cf02c0d8a..055b17004d 100644
--- a/includes/RtsAPI.h
+++ b/includes/RtsAPI.h
@@ -374,10 +374,6 @@ Capability *rts_unsafeGetMyCapability (void);
 // into Haskell.  The actual capability will be calculated as the supplied
 // value modulo the number of enabled Capabilities.
 //
-// Note that the thread may still be migrated by the RTS scheduler, but that
-// will only happen if there are multiple threads running on one Capability and
-// another Capability is free.
-//
 // If affinity is non-zero, the current thread will be bound to
 // specific CPUs according to the prevailing affinity policy for the
 // specified capability, set by either +RTS -qa or +RTS --numa.
@@ -479,6 +475,10 @@ void rts_evalLazyIO_ (/* inout */ Capability **,
                       /* in    */ unsigned int stack_size,
                       /* out   */ HaskellObj *ret);
 
+void rts_inCall (/* inout */ Capability **,
+                 /* in    */ HaskellObj p,
+                 /* out */   HaskellObj *ret);
+
 void rts_checkSchedStatus (char* site, Capability *);
 
 SchedulerStatus rts_getSchedStatus (Capability *cap);