path: root/rts/RtsAPI.c

/* ----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 1998-2001
 *
 * API for invoking Haskell functions via the RTS
 *
 * --------------------------------------------------------------------------*/

#include "PosixSource.h"
#include "Rts.h"
#include "RtsAPI.h"
#include "HsFFI.h"

#include "RtsUtils.h"
#include "Prelude.h"
#include "Schedule.h"
#include "Capability.h"
#include "StablePtr.h"
#include "Threads.h"
#include "Weak.h"

/* ----------------------------------------------------------------------------
   Building Haskell objects from C datatypes.

   TODO: Currently this code does not tag created pointers,
         however it is not unsafe (the constructor code will do it)
         just inefficient.
   ------------------------------------------------------------------------- */
HaskellObj
rts_mkChar (Capability *cap, HsChar c)
{
  StgClosure *p = (StgClosure *)allocate(cap, CONSTR_sizeW(0,1));
  SET_HDR(p, Czh_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)(StgWord)(StgChar)c;
  return p;
}

HaskellObj
rts_mkInt (Capability *cap, HsInt i)
{
  StgClosure *p = (StgClosure *)allocate(cap,CONSTR_sizeW(0,1));
  SET_HDR(p, Izh_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)(StgInt)i;
  return p;
}

HaskellObj
rts_mkInt8 (Capability *cap, HsInt8 i)
{
  StgClosure *p = (StgClosure *)allocate(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)i;
  return p;
}

HaskellObj
rts_mkInt16 (Capability *cap, HsInt16 i)
{
  StgClosure *p = (StgClosure *)allocate(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)i;
  return p;
}

HaskellObj
rts_mkInt32 (Capability *cap, HsInt32 i)
{
  StgClosure *p = (StgClosure *)allocate(cap,CONSTR_sizeW(0,1));
  SET_HDR(p, I32zh_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)(StgInt)i;
  return p;
}

HaskellObj
rts_mkInt64 (Capability *cap, HsInt64 i)
{
  StgClosure *p = (StgClosure *)allocate(cap,CONSTR_sizeW(0,2));
  SET_HDR(p, I64zh_con_info, CCS_SYSTEM);
  ASSIGN_Int64((P_)&(p->payload[0]), i);
  return p;
}

HaskellObj
rts_mkWord (Capability *cap, HsWord i)
{
  StgClosure *p = (StgClosure *)allocate(cap,CONSTR_sizeW(0,1));
  SET_HDR(p, Wzh_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)(StgWord)i;
  return p;
}

HaskellObj
rts_mkWord8 (Capability *cap, HsWord8 w)
{
  /* see rts_mkInt* comments */
  StgClosure *p = (StgClosure *)allocate(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 (Capability *cap, HsWord16 w)
{
  /* see rts_mkInt* comments */
  StgClosure *p = (StgClosure *)allocate(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 (Capability *cap, HsWord32 w)
{
  /* see rts_mkInt* comments */
  StgClosure *p = (StgClosure *)allocate(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 (Capability *cap, HsWord64 w)
{
  StgClosure *p = (StgClosure *)allocate(cap,CONSTR_sizeW(0,2));
  /* see mk_Int8 comment */
  SET_HDR(p, W64zh_con_info, CCS_SYSTEM);
  ASSIGN_Word64((P_)&(p->payload[0]), w);
  return p;
}


HaskellObj
rts_mkFloat (Capability *cap, HsFloat f)
{
  StgClosure *p = (StgClosure *)allocate(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 (Capability *cap, HsDouble d)
{
  StgClosure *p = (StgClosure *)allocate(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 (Capability *cap, HsStablePtr s)
{
  StgClosure *p = (StgClosure *)allocate(cap,sizeofW(StgHeader)+1);
  SET_HDR(p, StablePtr_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)s;
  return p;
}

HaskellObj
rts_mkPtr (Capability *cap, HsPtr a)
{
  StgClosure *p = (StgClosure *)allocate(cap,sizeofW(StgHeader)+1);
  SET_HDR(p, Ptr_con_info, CCS_SYSTEM);
  p->payload[0]  = (StgClosure *)a;
  return p;
}

HaskellObj
rts_mkFunPtr (Capability *cap, HsFunPtr a)
{
  StgClosure *p = (StgClosure *)allocate(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;
  } else {
    return (StgClosure *)False_closure;
  }
}

HaskellObj
rts_mkString (Capability *cap, char *s)
{
  return rts_apply(cap, (StgClosure *)unpackCString_closure, rts_mkPtr(cap,s));
}

HaskellObj
rts_apply (Capability *cap, HaskellObj f, HaskellObj arg)
{
    StgThunk *ap;

    ap = (StgThunk *)allocate(cap,sizeofW(StgThunk) + 2);
    // Here we don't want to use CCS_SYSTEM, because it's a hidden cost centre,
    // and evaluating Haskell code under a hidden cost centre leads to
    // confusing profiling output. (#7753)
    SET_HDR(ap, (StgInfoTable *)&stg_ap_2_upd_info, CCS_MAIN);
    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)
{
    // See comment above:
    // ASSERT(p->header.info == Czh_con_info ||
    //        p->header.info == Czh_static_info);
    return (StgChar)(StgWord)(UNTAG_CLOSURE(p)->payload[0]);
}

HsInt
rts_getInt (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == Izh_con_info ||
    //        p->header.info == Izh_static_info);
    return (HsInt)(UNTAG_CLOSURE(p)->payload[0]);
}

HsInt8
rts_getInt8 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == I8zh_con_info ||
    //        p->header.info == I8zh_static_info);
    return (HsInt8)(HsInt)(UNTAG_CLOSURE(p)->payload[0]);
}

HsInt16
rts_getInt16 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == I16zh_con_info ||
    //        p->header.info == I16zh_static_info);
    return (HsInt16)(HsInt)(UNTAG_CLOSURE(p)->payload[0]);
}

HsInt32
rts_getInt32 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == I32zh_con_info ||
    //        p->header.info == I32zh_static_info);
  return (HsInt32)(HsInt)(UNTAG_CLOSURE(p)->payload[0]);
}

HsInt64
rts_getInt64 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == I64zh_con_info ||
    //        p->header.info == I64zh_static_info);
    return PK_Int64((P_)&(UNTAG_CLOSURE(p)->payload[0]));
}

HsWord
rts_getWord (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == Wzh_con_info ||
    //        p->header.info == Wzh_static_info);
    return (HsWord)(UNTAG_CLOSURE(p)->payload[0]);
}

HsWord8
rts_getWord8 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == W8zh_con_info ||
    //        p->header.info == W8zh_static_info);
    return (HsWord8)(HsWord)(UNTAG_CLOSURE(p)->payload[0]);
}

HsWord16
rts_getWord16 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == W16zh_con_info ||
    //        p->header.info == W16zh_static_info);
    return (HsWord16)(HsWord)(UNTAG_CLOSURE(p)->payload[0]);
}

HsWord32
rts_getWord32 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == W32zh_con_info ||
    //        p->header.info == W32zh_static_info);
    return (HsWord32)(HsWord)(UNTAG_CLOSURE(p)->payload[0]);
}

HsWord64
rts_getWord64 (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == W64zh_con_info ||
    //        p->header.info == W64zh_static_info);
    return PK_Word64((P_)&(UNTAG_CLOSURE(p)->payload[0]));
}

HsFloat
rts_getFloat (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == Fzh_con_info ||
    //        p->header.info == Fzh_static_info);
    return (float)(PK_FLT((P_)UNTAG_CLOSURE(p)->payload));
}

HsDouble
rts_getDouble (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == Dzh_con_info ||
    //        p->header.info == Dzh_static_info);
    return (double)(PK_DBL((P_)UNTAG_CLOSURE(p)->payload));
}

HsStablePtr
rts_getStablePtr (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == StablePtr_con_info ||
    //        p->header.info == StablePtr_static_info);
    return (StgStablePtr)(UNTAG_CLOSURE(p)->payload[0]);
}

HsPtr
rts_getPtr (HaskellObj p)
{
    // See comment above:
    // ASSERT(p->header.info == Ptr_con_info ||
    //        p->header.info == Ptr_static_info);
    return (Capability *)(UNTAG_CLOSURE(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 *)(UNTAG_CLOSURE(p)->payload[0]);
}

HsBool
rts_getBool (HaskellObj p)
{
    const StgInfoTable *info;

    info = get_itbl((const StgClosure *)UNTAG_CONST_CLOSURE(p));
    if (info->srt == 0) { // srt is the constructor tag
        return 0;
    } else {
        return 1;
    }
}

/* -----------------------------------------------------------------------------
   Creating threads
   -------------------------------------------------------------------------- */

INLINE_HEADER void pushClosure   (StgTSO *tso, StgWord c) {
  tso->stackobj->sp--;
  tso->stackobj->sp[0] = (W_) c;
}

StgTSO *
createGenThread (Capability *cap, W_ stack_size,  StgClosure *closure)
{
  StgTSO *t;
  t = createThread (cap, stack_size);
  pushClosure(t, (W_)closure);
  pushClosure(t, (W_)&stg_enter_info);
  return t;
}

StgTSO *
createIOThread (Capability *cap, W_ stack_size,  StgClosure *closure)
{
  StgTSO *t;
  t = createThread (cap, stack_size);
  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, W_ stack_size,  StgClosure *closure)
{
  StgTSO *t;
  t = createThread(cap, stack_size);
  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;
}

/* ----------------------------------------------------------------------------
   Evaluating Haskell expressions
   ------------------------------------------------------------------------- */

void rts_eval (/* inout */ Capability **cap,
               /* in    */ HaskellObj p,
               /* out */   HaskellObj *ret)
{
    StgTSO *tso;

    tso = createGenThread(*cap, RtsFlags.GcFlags.initialStkSize, p);
    scheduleWaitThread(tso,ret,cap);
}

void rts_eval_ (/* inout */ Capability **cap,
                /* in    */ HaskellObj p,
                /* in    */ unsigned int stack_size,
                /* out   */ HaskellObj *ret)
{
    StgTSO *tso;

    tso = createGenThread(*cap, stack_size, p);
    scheduleWaitThread(tso,ret,cap);
}

/*
 * rts_evalIO() evaluates a value of the form (IO a), forcing the action's
 * result to WHNF before returning.
 */
void rts_evalIO (/* inout */ Capability **cap,
                 /* in    */ HaskellObj p,
                 /* out */   HaskellObj *ret)
{
    StgTSO* tso;

    tso = createStrictIOThread(*cap, RtsFlags.GcFlags.initialStkSize, p);
    scheduleWaitThread(tso,ret,cap);
}

/*
 * rts_evalStableIOMain() is suitable for calling main Haskell thread
 * stored in (StablePtr (IO a)) it calls rts_evalStableIO but wraps
 * function in GHC.TopHandler.runMainIO that installs top_handlers.
 * See #12903.
 */
void rts_evalStableIOMain(/* inout */ Capability **cap,
                          /* in    */ HsStablePtr s,
                          /* out   */ HsStablePtr *ret)
{
    StgTSO* tso;
    StgClosure *p, *r, *w;
    SchedulerStatus stat;

    p = (StgClosure *)deRefStablePtr(s);
    w = rts_apply(*cap, &base_GHCziTopHandler_runMainIO_closure, p);
    tso = createStrictIOThread(*cap, RtsFlags.GcFlags.initialStkSize, w);
    // async exceptions are always blocked by default in the created
    // thread.  See #1048.
    tso->flags |= TSO_BLOCKEX | TSO_INTERRUPTIBLE;
    scheduleWaitThread(tso,&r,cap);
    stat = rts_getSchedStatus(*cap);

    if (stat == Success && ret != NULL) {
        ASSERT(r != NULL);
        *ret = getStablePtr((StgPtr)r);
    }
}

/*
 * rts_evalStableIO() is suitable for calling from Haskell.  It
 * evaluates a value of the form (StablePtr (IO a)), forcing the
 * action's result to WHNF before returning.  The result is returned
 * in a StablePtr.
 */
void rts_evalStableIO (/* inout */ Capability **cap,
                       /* in    */ HsStablePtr s,
                       /* out */   HsStablePtr *ret)
{
    StgTSO* tso;
    StgClosure *p, *r;
    SchedulerStatus stat;

    p = (StgClosure *)deRefStablePtr(s);
    tso = createStrictIOThread(*cap, RtsFlags.GcFlags.initialStkSize, p);
    // async exceptions are always blocked by default in the created
    // thread.  See #1048.
    tso->flags |= TSO_BLOCKEX | TSO_INTERRUPTIBLE;
    scheduleWaitThread(tso,&r,cap);
    stat = rts_getSchedStatus(*cap);

    if (stat == Success && ret != NULL) {
        ASSERT(r != NULL);
        *ret = getStablePtr((StgPtr)r);
    }
}

/*
 * Like rts_evalIO(), but doesn't force the action's result.
 */
void rts_evalLazyIO (/* inout */ Capability **cap,
                     /* in    */ HaskellObj p,
                     /* out */   HaskellObj *ret)
{
    StgTSO *tso;

    tso = createIOThread(*cap, RtsFlags.GcFlags.initialStkSize, p);
    scheduleWaitThread(tso,ret,cap);
}

void rts_evalLazyIO_ (/* inout */ Capability **cap,
                      /* in    */ HaskellObj p,
                      /* in    */ unsigned int stack_size,
                      /* out   */ HaskellObj *ret)
{
    StgTSO *tso;

    tso = createIOThread(*cap, stack_size, p);
    scheduleWaitThread(tso,ret,cap);
}

/* Convenience function for decoding the returned status. */

void
rts_checkSchedStatus (char* site, Capability *cap)
{
    SchedulerStatus rc = cap->running_task->incall->rstat;
    switch (rc) {
    case Success:
        return;
    case Killed:
        errorBelch("%s: uncaught exception",site);
        stg_exit(EXIT_FAILURE);
    case Interrupted:
        errorBelch("%s: interrupted", site);
#if defined(THREADED_RTS)
        // The RTS is shutting down, and the process will probably
        // soon exit.  We don't want to preempt the shutdown
        // by exiting the whole process here, so we just terminate the
        // current thread.  Don't forget to release the cap first though.
        rts_unlock(cap);
        shutdownThread();
#else
        stg_exit(EXIT_FAILURE);
#endif
    default:
        errorBelch("%s: Return code (%d) not ok",(site),(rc));
        stg_exit(EXIT_FAILURE);
    }
}

SchedulerStatus
rts_getSchedStatus (Capability *cap)
{
    return cap->running_task->incall->rstat;
}

Capability *
rts_lock (void)
{
    Capability *cap;
    Task *task;

    task = newBoundTask();

    if (task->running_finalizers) {
        errorBelch("error: a C finalizer called back into Haskell.\n"
                   "   This was previously allowed, but is disallowed in GHC 6.10.2 and later.\n"
                   "   To create finalizers that may call back into Haskell, use\n"
                   "   Foreign.Concurrent.newForeignPtr instead of Foreign.newForeignPtr.");
        stg_exit(EXIT_FAILURE);
    }

    cap = NULL;
    waitForCapability(&cap, task);

    if (task->incall->prev_stack == NULL) {
      // This is a new outermost call from C into Haskell land.
      // Until the corresponding call to rts_unlock, this task
      // is doing work on behalf of the RTS.
      traceTaskCreate(task, cap);
    }

    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);

    // Now release the Capability.  With the capability released, GC
    // may happen.  NB. does not try to put the current Task on the
    // worker queue.
    // NB. keep cap->lock held while we call boundTaskExiting().  This
    // is necessary during shutdown, where we want the invariant that
    // after shutdownCapability(), all the Tasks associated with the
    // Capability have completed their shutdown too.  Otherwise we
    // could have boundTaskExiting()/workerTaskStop() running at some
    // random point in the future, which causes problems for
    // freeTaskManager().
    ACQUIRE_LOCK(&cap->lock);
    releaseCapability_(cap,false);

    // Finally, we can release the Task to the free list.
    boundTaskExiting(task);
    RELEASE_LOCK(&cap->lock);

    if (task->incall == NULL) {
      // This is the end of an outermost call from C into Haskell land.
      // From here on, the task goes back to C land and we should not count
      // it as doing work on behalf of the RTS.
      traceTaskDelete(task);
    }
}

void rts_done (void)
{
    freeMyTask();
}

/* -----------------------------------------------------------------------------
   tryPutMVar from outside Haskell

   The C call

      hs_try_putmvar(cap, mvar)

   is equivalent to the Haskell call

      tryPutMVar mvar ()

   but it is

     * non-blocking: takes a bounded, short, amount of time
     * asynchronous: the actual putMVar may be performed after the
       call returns.  That's why hs_try_putmvar() doesn't return a
       result to say whether the put succeeded.

   NOTE: this call transfers ownership of the StablePtr to the RTS, which will
   free it after the tryPutMVar has taken place.  The reason is that otherwise,
   it would be very difficult for the caller to arrange to free the StablePtr
   in all circumstances.

   For more details, see the section "Waking up Haskell threads from C" in the
   User's Guide.
   -------------------------------------------------------------------------- */

void hs_try_putmvar (/* in */ int capability,
                     /* in */ HsStablePtr mvar)
{
    Task *task = getTask();
    Capability *cap;
    Capability *task_old_cap USED_IF_THREADS;

    if (capability < 0) {
        capability = task->preferred_capability;
        if (capability < 0) {
            capability = 0;
        }
    }
    cap = capabilities[capability % enabled_capabilities];

#if !defined(THREADED_RTS)

    performTryPutMVar(cap, (StgMVar*)deRefStablePtr(mvar), Unit_closure);
    freeStablePtr(mvar);

#else

    ACQUIRE_LOCK(&cap->lock);
    // If the capability is free, we can perform the tryPutMVar immediately
    if (cap->running_task == NULL) {
        cap->running_task = task;
        task_old_cap = task->cap;
        task->cap = cap;
        RELEASE_LOCK(&cap->lock);

        performTryPutMVar(cap, (StgMVar*)deRefStablePtr(mvar), Unit_closure);

        freeStablePtr(mvar);

        // Wake up the capability, which will start running the thread that we
        // just awoke (if there was one).
        releaseCapability(cap);
        task->cap = task_old_cap;
    } else {
        PutMVar *p = stgMallocBytes(sizeof(PutMVar),"hs_try_putmvar");
        // We cannot deref the StablePtr if we don't have a capability,
        // so we have to store it and deref it later.
        p->mvar = mvar;
        p->link = cap->putMVars;
        cap->putMVars = p;
        RELEASE_LOCK(&cap->lock);
    }

#endif
}