// set_lwp_priority
//
// Set the priority of the lwp.  This call should only be made
// when using bound threads (T2 threads are bound by default).
//

int     set_lwp_priority (int ThreadID, int lwpid, int newPrio )
{

  {- -------------------------------------------
  (1) (変数宣言など)
      ---------------------------------------- -}

      int rslt;
      int Actual, Expected, prv;
      pcparms_t ParmInfo;                   // for GET-SET
    #ifdef ASSERT
      pcparms_t ReadBack;                   // for readback
    #endif

  {- -------------------------------------------
  (1) 
      ---------------------------------------- -}

      // Set priority via PC_GETPARMS, update, PC_SETPARMS
      // Query current values.
      // TODO: accelerate this by eliminating the PC_GETPARMS call.
      // Cache "pcparms_t" in global ParmCache.
      // TODO: elide set-to-same-value

  {- -------------------------------------------
  (1) もし初期化時に失敗していたら (= priocntl_enable 変数の値が false であれば), ここでリターン.
      (See: lwp_priocntl_init())

      (ついでに(トレース出力)も出している)
      ---------------------------------------- -}

      // If something went wrong on init, don't change priorities.
      if ( !priocntl_enable ) {
        if (ThreadPriorityVerbose)
          tty->print_cr("Trying to set priority but init failed, ignoring");
        return EINVAL;
      }


  {- -------------------------------------------
  (1) 引数で指定された lwp id が不正な場合, ここでリターン.
      (ついでに(トレース出力)も出している)
      ---------------------------------------- -}

      // If lwp hasn't started yet, just return
      // the _start routine will call us again.
      if ( lwpid <= 0 ) {
        if (ThreadPriorityVerbose) {
          tty->print_cr ("deferring the set_lwp_priority of thread " INTPTR_FORMAT " to %d, lwpid not set",
                         ThreadID, newPrio);
        }
        return 0;
      }

  {- -------------------------------------------
  (1) (トレース出力)
      ---------------------------------------- -}

      if (ThreadPriorityVerbose) {
        tty->print_cr ("set_lwp_priority(" INTPTR_FORMAT "@" INTPTR_FORMAT " %d) ",
                       ThreadID, lwpid, newPrio);
      }

  {- -------------------------------------------
  (1) (priocntl_ptr 変数経由で) priocntl() を呼び出して, 優先度情報(pcparms_t型のデータ)を取得する.
      失敗したらここでリターン.
      ---------------------------------------- -}

      memset(&ParmInfo, 0, sizeof(pcparms_t));
      ParmInfo.pc_cid = PC_CLNULL;
      rslt = (*priocntl_ptr)(PC_VERSION, P_LWPID, lwpid, PC_GETPARMS, (caddr_t)&ParmInfo);
      if (rslt < 0) return errno;

  {- -------------------------------------------
  (1) 取得した優先度情報を変更して, 新しい優先度に対応する優先度情報(pcparms_t型のデータ)を作成.
      ---------------------------------------- -}

      if (ParmInfo.pc_cid == rtLimits.schedPolicy) {
        rtparms_t *rtInfo  = (rtparms_t*)ParmInfo.pc_clparms;
        rtInfo->rt_pri     = scale_to_lwp_priority (rtLimits.minPrio, rtLimits.maxPrio, newPrio);
        rtInfo->rt_tqsecs  = RT_NOCHANGE;
        rtInfo->rt_tqnsecs = RT_NOCHANGE;
        if (ThreadPriorityVerbose) {
          tty->print_cr("RT: %d->%d\n", newPrio, rtInfo->rt_pri);
        }
      } else if (ParmInfo.pc_cid == iaLimits.schedPolicy) {
        iaparms_t *iaInfo  = (iaparms_t*)ParmInfo.pc_clparms;
        int maxClamped     = MIN2(iaLimits.maxPrio, (int)iaInfo->ia_uprilim);
        iaInfo->ia_upri    = scale_to_lwp_priority(iaLimits.minPrio, maxClamped, newPrio);
        iaInfo->ia_uprilim = IA_NOCHANGE;
        iaInfo->ia_mode    = IA_NOCHANGE;
        if (ThreadPriorityVerbose) {
          tty->print_cr ("IA: [%d...%d] %d->%d\n",
                   iaLimits.minPrio, maxClamped, newPrio, iaInfo->ia_upri);
        }
      } else if (ParmInfo.pc_cid == tsLimits.schedPolicy) {
        tsparms_t *tsInfo  = (tsparms_t*)ParmInfo.pc_clparms;
        int maxClamped     = MIN2(tsLimits.maxPrio, (int)tsInfo->ts_uprilim);
        prv                = tsInfo->ts_upri;
        tsInfo->ts_upri    = scale_to_lwp_priority(tsLimits.minPrio, maxClamped, newPrio);
        tsInfo->ts_uprilim = IA_NOCHANGE;
        if (ThreadPriorityVerbose) {
          tty->print_cr ("TS: %d [%d...%d] %d->%d\n",
                   prv, tsLimits.minPrio, maxClamped, newPrio, tsInfo->ts_upri);
        }
        if (prv == tsInfo->ts_upri) return 0;
      } else {
        if ( ThreadPriorityVerbose ) {
          tty->print_cr ("Unknown scheduling class\n");
        }
          return EINVAL;    // no clue, punt
      }

  {- -------------------------------------------
  (1) (priocntl_ptr 変数経由で) priocntl() を呼び出して, 優先度を変更する.
      失敗したらここでリターン.
      ---------------------------------------- -}

      rslt = (*priocntl_ptr)(PC_VERSION, P_LWPID, lwpid, PC_SETPARMS, (caddr_t)&ParmInfo);
      if (ThreadPriorityVerbose && rslt) {
        tty->print_cr ("PC_SETPARMS ->%d %d\n", rslt, errno);
      }
      if (rslt < 0) return errno;

  {- -------------------------------------------
  (1) (デバッグ用の処理) (#ifdef ASSERT 時にのみ実行)
      ---------------------------------------- -}

    #ifdef ASSERT
      // Sanity check: read back what we just attempted to set.
      // In theory it could have changed in the interim ...
      //
      // The priocntl system call is tricky.
      // Sometimes it'll validate the priority value argument and
      // return EINVAL if unhappy.  At other times it fails silently.
      // Readbacks are prudent.

      if (!ReadBackValidate) return 0;

      memset(&ReadBack, 0, sizeof(pcparms_t));
      ReadBack.pc_cid = PC_CLNULL;
      rslt = (*priocntl_ptr)(PC_VERSION, P_LWPID, lwpid, PC_GETPARMS, (caddr_t)&ReadBack);
      assert(rslt >= 0, "priocntl failed");
      Actual = Expected = 0xBAD;
      assert(ParmInfo.pc_cid == ReadBack.pc_cid, "cid's don't match");
      if (ParmInfo.pc_cid == rtLimits.schedPolicy) {
        Actual   = RTPRI(ReadBack)->rt_pri;
        Expected = RTPRI(ParmInfo)->rt_pri;
      } else if (ParmInfo.pc_cid == iaLimits.schedPolicy) {
        Actual   = IAPRI(ReadBack)->ia_upri;
        Expected = IAPRI(ParmInfo)->ia_upri;
      } else if (ParmInfo.pc_cid == tsLimits.schedPolicy) {
        Actual   = TSPRI(ReadBack)->ts_upri;
        Expected = TSPRI(ParmInfo)->ts_upri;
      } else {
        if ( ThreadPriorityVerbose ) {
          tty->print_cr("set_lwp_priority: unexpected class in readback: %d\n", ParmInfo.pc_cid);
        }
      }

      if (Actual != Expected) {
        if ( ThreadPriorityVerbose ) {
          tty->print_cr ("set_lwp_priority(%d %d) Class=%d: actual=%d vs expected=%d\n",
                 lwpid, newPrio, ReadBack.pc_cid, Actual, Expected);
        }
      }
    #endif

  {- -------------------------------------------
  (1) リターン
      ---------------------------------------- -}

      return 0;
    }