X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Frts%2FRtsAPI.c;h=b1b1d9c52d7f4c4e53e87547039887ad065e5107;hb=c56641e7752db313effe332b81f9e56275342fbd;hp=cd0ef4c577671a1d3a5118bc441df8a5e8923b84;hpb=7543711db25a39cff8c19d4bdf02639255f1912f;p=ghc-hetmet.git

diff --git a/ghc/rts/RtsAPI.c b/ghc/rts/RtsAPI.c
index cd0ef4c..b1b1d9c 100644
--- a/ghc/rts/RtsAPI.c
+++ b/ghc/rts/RtsAPI.c
@@ -1,5 +1,4 @@
 /* ----------------------------------------------------------------------------
- * $Id: RtsAPI.c,v 1.34 2002/04/13 05:28:04 sof Exp $
  *
  * (c) The GHC Team, 1998-2001
  *
@@ -9,92 +8,43 @@
 
 #include "PosixSource.h"
 #include "Rts.h"
+#include "OSThreads.h"
 #include "Storage.h"
 #include "RtsAPI.h"
 #include "SchedAPI.h"
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "Prelude.h"
-#include "OSThreads.h"
 #include "Schedule.h"
+#include "Capability.h"
 
-#if defined(THREADED_RTS)
-#define WAIT_MAIN_THREAD(tso,ret) waitThread_(tso,ret,rtsFalse)
-#define WAIT_EXT_THREAD(tso,ret) waitThread_(tso,ret,rtsTrue)
-#else
-#define WAIT_MAIN_THREAD(tso,ret) waitThread(tso,ret)
-#define WAIT_EXT_THREAD(tso,ret) waitThread(tso,ret)
-#endif
-
-#if defined(RTS_SUPPORTS_THREADS)
-/* Cheesy locking scheme while waiting for the 
- * RTS API to change.
- */
-static Mutex     alloc_mutex = INIT_MUTEX_VAR;
-static Condition alloc_cond  = INIT_COND_VAR;
-#define INVALID_THREAD_ID ((OSThreadId)(-1))
-
-/* Thread currently owning the allocator */
-static OSThreadId c_id = INVALID_THREAD_ID;
-
-static StgPtr alloc(nat n)
-{
-  OSThreadId tid = osThreadId();
-  ACQUIRE_LOCK(&alloc_mutex);
-  if (tid == c_id) {
-    /* I've got the lock, just allocate() */
-    ;
-  } else if (c_id == INVALID_THREAD_ID) {
-    c_id = tid;
-  } else {
-    waitCondition(&alloc_cond, &alloc_mutex);
-    c_id = tid;
-  }
-  RELEASE_LOCK(&alloc_mutex);
-  return allocate(n);
-}
-
-static void releaseAllocLock(void)
-{
-  ACQUIRE_LOCK(&alloc_mutex);
-  /* Reset the allocator owner */
-  c_id = INVALID_THREAD_ID;
-  RELEASE_LOCK(&alloc_mutex);
-
-  /* Free up an OS thread waiting to get in */
-  signalCondition(&alloc_cond);
-}
-#else
-# define alloc(n) allocate(n)
-# define releaseAllocLock() /* nothing */
-#endif
-
+#include <stdlib.h>
 
 /* ----------------------------------------------------------------------------
    Building Haskell objects from C datatypes.
    ------------------------------------------------------------------------- */
 HaskellObj
-rts_mkChar (HsChar c)
+rts_mkChar (Capability *cap, HsChar c)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap, CONSTR_sizeW(0,1));
   SET_HDR(p, Czh_con_info, CCS_SYSTEM);
-  p->payload[0]  = (StgClosure *)(StgChar)c;
+  p->payload[0]  = (StgClosure *)(StgWord)(StgChar)c;
   return p;
 }
 
 HaskellObj
-rts_mkInt (HsInt i)
+rts_mkInt (Capability *cap, HsInt i)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, Izh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgInt)i;
   return p;
 }
 
 HaskellObj
-rts_mkInt8 (HsInt8 i)
+rts_mkInt8 (Capability *cap, HsInt8 i)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, I8zh_con_info, CCS_SYSTEM);
   /* Make sure we mask out the bits above the lowest 8 */
   p->payload[0]  = (StgClosure *)(StgInt)((unsigned)i & 0xff);
@@ -102,9 +52,9 @@ rts_mkInt8 (HsInt8 i)
 }
 
 HaskellObj
-rts_mkInt16 (HsInt16 i)
+rts_mkInt16 (Capability *cap, HsInt16 i)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, I16zh_con_info, CCS_SYSTEM);
   /* Make sure we mask out the relevant bits */
   p->payload[0]  = (StgClosure *)(StgInt)((unsigned)i & 0xffff);
@@ -112,116 +62,124 @@ rts_mkInt16 (HsInt16 i)
 }
 
 HaskellObj
-rts_mkInt32 (HsInt32 i)
+rts_mkInt32 (Capability *cap, HsInt32 i)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, I32zh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgInt)((unsigned)i & 0xffffffff);
   return p;
 }
 
 HaskellObj
-rts_mkInt64 (HsInt64 i)
+rts_mkInt64 (Capability *cap, HsInt64 i)
 {
-  long long *tmp;
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,2));
+  llong *tmp;
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,2));
   SET_HDR(p, I64zh_con_info, CCS_SYSTEM);
-  tmp  = (long long*)&(p->payload[0]);
+  tmp  = (llong*)&(p->payload[0]);
   *tmp = (StgInt64)i;
   return p;
 }
 
 HaskellObj
-rts_mkWord (HsWord i)
+rts_mkWord (Capability *cap, HsWord i)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, Wzh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgWord)i;
   return p;
 }
 
 HaskellObj
-rts_mkWord8 (HsWord8 w)
+rts_mkWord8 (Capability *cap, HsWord8 w)
 {
   /* see rts_mkInt* comments */
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, W8zh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgWord)(w & 0xff);
   return p;
 }
 
 HaskellObj
-rts_mkWord16 (HsWord16 w)
+rts_mkWord16 (Capability *cap, HsWord16 w)
 {
   /* see rts_mkInt* comments */
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, W16zh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgWord)(w & 0xffff);
   return p;
 }
 
 HaskellObj
-rts_mkWord32 (HsWord32 w)
+rts_mkWord32 (Capability *cap, HsWord32 w)
 {
   /* see rts_mkInt* comments */
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, W32zh_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)(StgWord)(w & 0xffffffff);
   return p;
 }
 
 HaskellObj
-rts_mkWord64 (HsWord64 w)
+rts_mkWord64 (Capability *cap, HsWord64 w)
 {
-  unsigned long long *tmp;
+  ullong *tmp;
 
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,2));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,2));
   /* see mk_Int8 comment */
   SET_HDR(p, W64zh_con_info, CCS_SYSTEM);
-  tmp  = (unsigned long long*)&(p->payload[0]);
+  tmp  = (ullong*)&(p->payload[0]);
   *tmp = (StgWord64)w;
   return p;
 }
 
 HaskellObj
-rts_mkFloat (HsFloat f)
+rts_mkFloat (Capability *cap, HsFloat f)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,1));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,1));
   SET_HDR(p, Fzh_con_info, CCS_SYSTEM);
   ASSIGN_FLT((P_)p->payload, (StgFloat)f);
   return p;
 }
 
 HaskellObj
-rts_mkDouble (HsDouble d)
+rts_mkDouble (Capability *cap, HsDouble d)
 {
-  StgClosure *p = (StgClosure *)alloc(CONSTR_sizeW(0,sizeofW(StgDouble)));
+  StgClosure *p = (StgClosure *)allocateLocal(cap,CONSTR_sizeW(0,sizeofW(StgDouble)));
   SET_HDR(p, Dzh_con_info, CCS_SYSTEM);
   ASSIGN_DBL((P_)p->payload, (StgDouble)d);
   return p;
 }
 
 HaskellObj
-rts_mkStablePtr (HsStablePtr s)
+rts_mkStablePtr (Capability *cap, HsStablePtr s)
 {
-  StgClosure *p = (StgClosure *)alloc(sizeofW(StgHeader)+1);
+  StgClosure *p = (StgClosure *)allocateLocal(cap,sizeofW(StgHeader)+1);
   SET_HDR(p, StablePtr_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)s;
   return p;
 }
 
 HaskellObj
-rts_mkPtr (HsPtr a)
+rts_mkPtr (Capability *cap, HsPtr a)
 {
-  StgClosure *p = (StgClosure *)alloc(sizeofW(StgHeader)+1);
+  StgClosure *p = (StgClosure *)allocateLocal(cap,sizeofW(StgHeader)+1);
   SET_HDR(p, Ptr_con_info, CCS_SYSTEM);
   p->payload[0]  = (StgClosure *)a;
   return p;
 }
 
-#ifdef COMPILER /* GHC has em, Hugs doesn't */
 HaskellObj
-rts_mkBool (HsBool b)
+rts_mkFunPtr (Capability *cap, HsFunPtr a)
+{
+  StgClosure *p = (StgClosure *)allocateLocal(cap,sizeofW(StgHeader)+1);
+  SET_HDR(p, FunPtr_con_info, CCS_SYSTEM);
+  p->payload[0]  = (StgClosure *)a;
+  return p;
+}
+
+HaskellObj
+rts_mkBool (Capability *cap STG_UNUSED, HsBool b)
 {
   if (b) {
     return (StgClosure *)True_closure;
@@ -231,273 +189,287 @@ rts_mkBool (HsBool b)
 }
 
 HaskellObj
-rts_mkString (char *s)
+rts_mkString (Capability *cap, char *s)
 {
-  return rts_apply((StgClosure *)unpackCString_closure, rts_mkPtr(s));
+  return rts_apply(cap, (StgClosure *)unpackCString_closure, rts_mkPtr(cap,s));
 }
-#endif /* COMPILER */
 
 HaskellObj
-rts_apply (HaskellObj f, HaskellObj arg)
+rts_apply (Capability *cap, HaskellObj f, HaskellObj arg)
 {
-  StgAP_UPD *ap = (StgAP_UPD *)alloc(AP_sizeW(1));
-  SET_HDR(ap, &stg_AP_UPD_info, CCS_SYSTEM);
-  ap->n_args = 1;
-  ap->fun    = f;
-  ap->payload[0] = arg;
-  return (StgClosure *)ap;
+    StgThunk *ap;
+
+    ap = (StgThunk *)allocateLocal(cap,sizeofW(StgThunk) + 2);
+    SET_HDR(ap, (StgInfoTable *)&stg_ap_2_upd_info, CCS_SYSTEM);
+    ap->payload[0] = f;
+    ap->payload[1] = arg;
+    return (StgClosure *)ap;
 }
 
 /* ----------------------------------------------------------------------------
    Deconstructing Haskell objects
+
+   We would like to assert that we have the right kind of object in
+   each case, but this is problematic because in GHCi the info table
+   for the D# constructor (say) might be dynamically loaded.  Hence we
+   omit these assertions for now.
    ------------------------------------------------------------------------- */
 
 HsChar
 rts_getChar (HaskellObj p)
 {
-  if ( p->header.info == Czh_con_info || 
-       p->header.info == Czh_static_info) {
+    // See comment above:
+    // ASSERT(p->header.info == Czh_con_info ||
+    //        p->header.info == Czh_static_info);
     return (StgChar)(StgWord)(p->payload[0]);
-  } else {
-    barf("rts_getChar: not a Char");
-  }
 }
 
 HsInt
 rts_getInt (HaskellObj p)
 {
-  if ( 1 ||
-       p->header.info == Izh_con_info || 
-       p->header.info == Izh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == Izh_con_info ||
+    //        p->header.info == Izh_static_info);
     return (HsInt)(p->payload[0]);
-  } else {
-    barf("rts_getInt: not an Int");
-  }
 }
 
 HsInt8
 rts_getInt8 (HaskellObj p)
 {
-  if ( 1 ||
-       p->header.info == I8zh_con_info || 
-       p->header.info == I8zh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == I8zh_con_info ||
+    //        p->header.info == I8zh_static_info);
     return (HsInt8)(HsInt)(p->payload[0]);
-  } else {
-    barf("rts_getInt8: not an Int8");
-  }
 }
 
 HsInt16
 rts_getInt16 (HaskellObj p)
 {
-  if ( 1 ||
-       p->header.info == I16zh_con_info || 
-       p->header.info == I16zh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == I16zh_con_info ||
+    //        p->header.info == I16zh_static_info);
     return (HsInt16)(HsInt)(p->payload[0]);
-  } else {
-    barf("rts_getInt16: not an Int16");
-  }
 }
 
 HsInt32
 rts_getInt32 (HaskellObj p)
 {
-  if ( 1 ||
-       p->header.info == I32zh_con_info || 
-       p->header.info == I32zh_static_info ) {
-    return (HsInt32)(p->payload[0]);
-  } else {
-    barf("rts_getInt32: not an Int32");
-  }
+    // See comment above:
+    // ASSERT(p->header.info == I32zh_con_info ||
+    //        p->header.info == I32zh_static_info);
+    return (HsInt32)(HsInt)(p->payload[0]);
 }
 
 HsInt64
 rts_getInt64 (HaskellObj p)
 {
-  HsInt64* tmp;
-  if ( 1 ||
-       p->header.info == I64zh_con_info || 
-       p->header.info == I64zh_static_info ) {
+    HsInt64* tmp;
+    // See comment above:
+    // ASSERT(p->header.info == I64zh_con_info ||
+    //        p->header.info == I64zh_static_info);
     tmp = (HsInt64*)&(p->payload[0]);
     return *tmp;
-  } else {
-    barf("rts_getInt64: not an Int64");
-  }
 }
 HsWord
 rts_getWord (HaskellObj p)
 {
-  if ( 1 || /* see above comment */
-       p->header.info == Wzh_con_info ||
-       p->header.info == Wzh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == Wzh_con_info ||
+    //        p->header.info == Wzh_static_info);
     return (HsWord)(p->payload[0]);
-  } else {
-    barf("rts_getWord: not a Word");
-  }
 }
 
 HsWord8
 rts_getWord8 (HaskellObj p)
 {
-  if ( 1 || /* see above comment */
-       p->header.info == W8zh_con_info ||
-       p->header.info == W8zh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == W8zh_con_info ||
+    //        p->header.info == W8zh_static_info);
     return (HsWord8)(HsWord)(p->payload[0]);
-  } else {
-    barf("rts_getWord8: not a Word8");
-  }
 }
 
 HsWord16
 rts_getWord16 (HaskellObj p)
 {
-  if ( 1 || /* see above comment */
-       p->header.info == W16zh_con_info ||
-       p->header.info == W16zh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == W16zh_con_info ||
+    //        p->header.info == W16zh_static_info);
     return (HsWord16)(HsWord)(p->payload[0]);
-  } else {
-    barf("rts_getWord16: not a Word16");
-  }
 }
 
 HsWord32
 rts_getWord32 (HaskellObj p)
 {
-  if ( 1 || /* see above comment */
-       p->header.info == W32zh_con_info ||
-       p->header.info == W32zh_static_info ) {
-    return (unsigned int)(p->payload[0]);
-  } else {
-    barf("rts_getWord: not a Word");
-  }
+    // See comment above:
+    // ASSERT(p->header.info == W32zh_con_info ||
+    //        p->header.info == W32zh_static_info);
+    return (HsWord32)(HsWord)(p->payload[0]);
 }
 
 
 HsWord64
 rts_getWord64 (HaskellObj p)
 {
-  HsWord64* tmp;
-  if ( 1 || /* see above comment */
-       p->header.info == W64zh_con_info ||
-       p->header.info == W64zh_static_info ) {
+    HsWord64* tmp;
+    // See comment above:
+    // ASSERT(p->header.info == W64zh_con_info ||
+    //        p->header.info == W64zh_static_info);
     tmp = (HsWord64*)&(p->payload[0]);
     return *tmp;
-  } else {
-    barf("rts_getWord64: not a Word64");
-  }
 }
 
 HsFloat
 rts_getFloat (HaskellObj p)
 {
-  if ( p->header.info == Fzh_con_info || 
-       p->header.info == Fzh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == Fzh_con_info ||
+    //        p->header.info == Fzh_static_info);
     return (float)(PK_FLT((P_)p->payload));
-  } else {
-    barf("rts_getFloat: not a Float");
-  }
 }
 
 HsDouble
 rts_getDouble (HaskellObj p)
 {
-  if ( p->header.info == Dzh_con_info || 
-       p->header.info == Dzh_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == Dzh_con_info ||
+    //        p->header.info == Dzh_static_info);
     return (double)(PK_DBL((P_)p->payload));
-  } else {
-    barf("rts_getDouble: not a Double");
-  }
 }
 
 HsStablePtr
 rts_getStablePtr (HaskellObj p)
 {
-  if ( p->header.info == StablePtr_con_info || 
-       p->header.info == StablePtr_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == StablePtr_con_info ||
+    //        p->header.info == StablePtr_static_info);
     return (StgStablePtr)(p->payload[0]);
-  } else {
-    barf("rts_getStablePtr: not a StablePtr");
-  }
 }
 
 HsPtr
 rts_getPtr (HaskellObj p)
 {
-  if ( p->header.info == Ptr_con_info || 
-       p->header.info == Ptr_static_info ) {
+    // See comment above:
+    // ASSERT(p->header.info == Ptr_con_info ||
+    //        p->header.info == Ptr_static_info);
+    return (Capability *)(p->payload[0]);
+}
+
+HsFunPtr
+rts_getFunPtr (HaskellObj p)
+{
+    // See comment above:
+    // ASSERT(p->header.info == FunPtr_con_info ||
+    //        p->header.info == FunPtr_static_info);
     return (void *)(p->payload[0]);
-  } else {
-    barf("rts_getPtr: not an Ptr");
-  }
 }
 
-#ifdef COMPILER /* GHC has em, Hugs doesn't */
 HsBool
 rts_getBool (HaskellObj p)
 {
-  if (p == True_closure) {
-    return 1;
-  } else if (p == False_closure) {
-    return 0;
-  } else {
-    barf("rts_getBool: not a Bool");
-  }
+    StgInfoTable *info;
+
+    info = get_itbl((StgClosure *)p);
+    if (info->srt_bitmap == 0) { // srt_bitmap is the constructor tag
+	return 0;
+    } else {
+	return 1;
+    }
+}
+
+/* -----------------------------------------------------------------------------
+   Creating threads
+   -------------------------------------------------------------------------- */
+
+INLINE_HEADER void pushClosure   (StgTSO *tso, StgWord c) {
+  tso->sp--;
+  tso->sp[0] = (W_) c;
+}
+
+StgTSO *
+createGenThread (Capability *cap, nat stack_size,  StgClosure *closure)
+{
+  StgTSO *t;
+#if defined(GRAN)
+  t = createThread (cap, stack_size, NO_PRI);
+#else
+  t = createThread (cap, stack_size);
+#endif
+  pushClosure(t, (W_)closure);
+  pushClosure(t, (W_)&stg_enter_info);
+  return t;
+}
+
+StgTSO *
+createIOThread (Capability *cap, nat stack_size,  StgClosure *closure)
+{
+  StgTSO *t;
+#if defined(GRAN)
+  t = createThread (cap, stack_size, NO_PRI);
+#else
+  t = createThread (cap, stack_size);
+#endif
+  pushClosure(t, (W_)&stg_noforceIO_info);
+  pushClosure(t, (W_)&stg_ap_v_info);
+  pushClosure(t, (W_)closure);
+  pushClosure(t, (W_)&stg_enter_info);
+  return t;
+}
+
+/*
+ * Same as above, but also evaluate the result of the IO action
+ * to whnf while we're at it.
+ */
+
+StgTSO *
+createStrictIOThread(Capability *cap, nat stack_size,  StgClosure *closure)
+{
+  StgTSO *t;
+#if defined(GRAN)
+  t = createThread(cap, stack_size, NO_PRI);
+#else
+  t = createThread(cap, stack_size);
+#endif
+  pushClosure(t, (W_)&stg_forceIO_info);
+  pushClosure(t, (W_)&stg_ap_v_info);
+  pushClosure(t, (W_)closure);
+  pushClosure(t, (W_)&stg_enter_info);
+  return t;
 }
-#endif /* COMPILER */
 
 /* ----------------------------------------------------------------------------
    Evaluating Haskell expressions
    ------------------------------------------------------------------------- */
-SchedulerStatus
-rts_eval (HaskellObj p, /*out*/HaskellObj *ret)
+
+Capability *
+rts_eval (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret)
 {
     StgTSO *tso;
-
-    tso = createGenThread(RtsFlags.GcFlags.initialStkSize, p);
-    releaseAllocLock();
-    scheduleExtThread(tso);
-    return WAIT_EXT_THREAD(tso, ret);
+    
+    tso = createGenThread(cap, RtsFlags.GcFlags.initialStkSize, p);
+    return scheduleWaitThread(tso,ret,cap);
 }
 
-SchedulerStatus
-rts_eval_ (HaskellObj p, unsigned int stack_size, /*out*/HaskellObj *ret)
+Capability *
+rts_eval_ (Capability *cap, HaskellObj p, unsigned int stack_size, 
+	   /*out*/HaskellObj *ret)
 {
     StgTSO *tso;
-    
-    tso = createGenThread(stack_size, p);
-    releaseAllocLock();
-    scheduleExtThread(tso);
-    return WAIT_EXT_THREAD(tso, ret);
+
+    tso = createGenThread(cap, stack_size, p);
+    return scheduleWaitThread(tso,ret,cap);
 }
 
 /*
  * rts_evalIO() evaluates a value of the form (IO a), forcing the action's
  * result to WHNF before returning.
  */
-SchedulerStatus
-rts_evalIO (HaskellObj p, /*out*/HaskellObj *ret)
-{
-    StgTSO* tso; 
-    
-    tso = createStrictIOThread(RtsFlags.GcFlags.initialStkSize, p);
-    releaseAllocLock();
-    scheduleExtThread(tso);
-    return WAIT_EXT_THREAD(tso, ret);
-}
-
-/*
- * Identical to rts_evalIO(), but won't create a new task/OS thread
- * to evaluate the Haskell thread. Used by main() only. Hack.
- */
-SchedulerStatus
-rts_mainEvalIO(HaskellObj p, /*out*/HaskellObj *ret)
+Capability *
+rts_evalIO (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret)
 {
     StgTSO* tso; 
     
-    tso = createStrictIOThread(RtsFlags.GcFlags.initialStkSize, p);
-    releaseAllocLock();
-    scheduleThread(tso);
-    return WAIT_MAIN_THREAD(tso, ret);
+    tso = createStrictIOThread(cap, RtsFlags.GcFlags.initialStkSize, p);
+    return scheduleWaitThread(tso,ret,cap);
 }
 
 /*
@@ -506,54 +478,120 @@ rts_mainEvalIO(HaskellObj p, /*out*/HaskellObj *ret)
  * action's result to WHNF before returning.  The result is returned
  * in a StablePtr.
  */
-SchedulerStatus
-rts_evalStableIO (HsStablePtr s, /*out*/HsStablePtr *ret)
+Capability *
+rts_evalStableIO (Capability *cap, HsStablePtr s, /*out*/HsStablePtr *ret)
 {
     StgTSO* tso;
     StgClosure *p, *r;
     SchedulerStatus stat;
     
     p = (StgClosure *)deRefStablePtr(s);
-    tso = createStrictIOThread(RtsFlags.GcFlags.initialStkSize, p);
-    releaseAllocLock();
-    scheduleExtThread(tso);
-    stat = WAIT_EXT_THREAD(tso, &r);
+    tso = createStrictIOThread(cap, RtsFlags.GcFlags.initialStkSize, p);
+    cap = scheduleWaitThread(tso,&r,cap);
+    stat = rts_getSchedStatus(cap);
 
-    if (stat == Success) {
+    if (stat == Success && ret != NULL) {
 	ASSERT(r != NULL);
 	*ret = getStablePtr((StgPtr)r);
     }
 
-    return stat;
+    return cap;
 }
 
 /*
  * Like rts_evalIO(), but doesn't force the action's result.
  */
-SchedulerStatus
-rts_evalLazyIO (HaskellObj p, unsigned int stack_size, /*out*/HaskellObj *ret)
+Capability *
+rts_evalLazyIO (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret)
+{
+    StgTSO *tso;
+
+    tso = createIOThread(cap, RtsFlags.GcFlags.initialStkSize, p);
+    return scheduleWaitThread(tso,ret,cap);
+}
+
+Capability *
+rts_evalLazyIO_ (Capability *cap, HaskellObj p, unsigned int stack_size, 
+		 /*out*/HaskellObj *ret)
 {
     StgTSO *tso;
 
-    tso = createIOThread(stack_size, p);
-    releaseAllocLock();
-    scheduleExtThread(tso);
-    return WAIT_EXT_THREAD(tso, ret);
+    tso = createIOThread(cap, stack_size, p);
+    return scheduleWaitThread(tso,ret,cap);
 }
 
 /* Convenience function for decoding the returned status. */
 
 void
-rts_checkSchedStatus ( char* site, SchedulerStatus rc )
+rts_checkSchedStatus (char* site, Capability *cap)
 {
+    SchedulerStatus rc = cap->running_task->stat;
     switch (rc) {
     case Success:
 	return;
     case Killed:
-	barf("%s: uncaught exception",site);
+	errorBelch("%s: uncaught exception",site);
+	stg_exit(EXIT_FAILURE);
     case Interrupted:
-	barf("%s: interrupted", site);
+	errorBelch("%s: interrupted", site);
+	stg_exit(EXIT_FAILURE);
     default:
-	barf("%s: Return code (%d) not ok",(site),(rc));	
+	errorBelch("%s: Return code (%d) not ok",(site),(rc));	
+	stg_exit(EXIT_FAILURE);
     }
 }
+
+SchedulerStatus
+rts_getSchedStatus (Capability *cap)
+{
+    return cap->running_task->stat;
+}
+
+Capability *
+rts_lock (void)
+{
+    Capability *cap;
+    Task *task;
+
+    // ToDo: get rid of this lock in the common case.  We could store
+    // a free Task in thread-local storage, for example.  That would
+    // leave just one lock on the path into the RTS: cap->lock when
+    // acquiring the Capability.
+    ACQUIRE_LOCK(&sched_mutex);
+    task = newBoundTask();
+    RELEASE_LOCK(&sched_mutex);
+
+    cap = NULL;
+    waitForReturnCapability(&cap, task);
+    return (Capability *)cap;
+}
+
+// Exiting the RTS: we hold a Capability that is not necessarily the
+// same one that was originally returned by rts_lock(), because
+// rts_evalIO() etc. may return a new one.  Now that we have
+// investigated the return value, we can release the Capability,
+// and free the Task (in that order).
+
+void
+rts_unlock (Capability *cap)
+{
+    Task *task;
+
+    task = cap->running_task;
+    ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
+
+    // slightly delicate ordering of operations below, pay attention!
+
+    // We are no longer a bound task/thread.  This is important,
+    // because the GC can run when we release the Capability below,
+    // and we don't want it to treat this as a live TSO pointer.
+    task->tso = NULL;
+
+    // Now release the Capability.  With the capability released, GC
+    // may happen.  NB. does not try to put the current Task on the
+    // worker queue.
+    releaseCapability(cap);
+
+    // Finally, we can release the Task to the free list.
+    boundTaskExiting(task);
+}