RTS: Add setInCallCapability()

This allows an OS thread to specify which capability it should run on
when it makes a call into Haskell.  It is intended for a fairly
specialised use case, when the client wants to have tighter control over
the mapping between OS threads and Capabilities - perhaps 1:1
correspondence, for example.

1 files changed, 3 insertions, 0 deletions

diff --git a/rts/Task.h b/rts/Task.h
index 37832a39d3..bcf456d270 100644
--- a/rts/Task.h
+++ b/rts/Task.h
@@ -151,6 +151,9 @@ typedef struct Task_ {
     // So that we can detect when a finalizer illegally calls back into Haskell
     rtsBool running_finalizers;
 
+    // if >= 0, this Capability will be used for in-calls
+    int preferred_capability;
+
     // Links tasks on the returning_tasks queue of a Capability, and
     // on spare_workers.
     struct Task_ *next;