rom/exec/wait.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Wait for some signal.
   6     Lang: english
   7 */
   8 #include <exec/execbase.h>
   9 #include <aros/libcall.h>
  10 #include <proto/exec.h>
  11
  12 /*****************************************************************************
  13
  14     NAME */
  15
  16         AROS_LH1(ULONG, Wait,
  17
  18 /*  SYNOPSIS */
  19         AROS_LHA(ULONG, signalSet, D0),
  20
  21 /*  LOCATION */
  22         struct ExecBase *, SysBase, 53, Exec)
  23
  24 /*  FUNCTION
  25         Wait until some signals are sent to the current task. If any signal
  26         of the specified set is already set when entering this function it
  27         returns immediately. Since almost any event in the OS can send a
  28         signal to your task if you specify it to do so signals are a very
  29         powerful mechanism.
  30
  31     INPUTS
  32         signalSet - The set of signals to wait for.
  33
  34     RESULT
  35         The set of active signals.
  36
  37     NOTES
  38         Naturally it's not allowed to wait in supervisor mode.
  39
  40         Calling Wait() breaks an active Disable() or Forbid().
  41
  42     EXAMPLE
  43
  44     BUGS
  45
  46     SEE ALSO
  47         Signal(), SetSignal(), AllocSignal(), FreeSignal()
  48
  49     INTERNALS
  50
  51 ******************************************************************************/
  52 {
  53     AROS_LIBFUNC_INIT
  54
  55     ULONG rcvd;
  56     struct Task *me;
  57
  58     /* Get pointer to current task - I'll need it very often */
  59     me = FindTask (NULL);
  60
  61     /* Protect the task lists against access by other tasks. */
  62     Disable();
  63
  64     /* If at least one of the signals is already set do not wait. */
  65     while(!(me->tc_SigRecvd&signalSet))
  66     {
  67         BYTE old_TDNestCnt;
  68
  69         /* Set the wait signal mask */
  70         me->tc_SigWait=signalSet;
  71
  72         /*
  73             Clear TDNestCnt (because Switch() will not care about it),
  74             but memorize it first. IDNestCnt is handled by Switch().
  75             This could as well be stored in a local variable which makes
  76             the tc_TDNestCnt field somehow redundant.
  77         */
  78         old_TDNestCnt=SysBase->TDNestCnt;
  79         SysBase->TDNestCnt=-1;
  80
  81         /* Move current task to the waiting list. */
  82         me->tc_State=TS_WAIT;
  83         Enqueue(&SysBase->TaskWait,&me->tc_Node);
  84
  85         /* And switch to the next ready task. */
  86         Switch();
  87         /*
  88             OK. Somebody awakened me. This means that either the
  89             signals are there or it's just a finished task exception.
  90             Test again to be sure (see above).
  91         */
  92
  93         /* Restore TDNestCnt. */
  94         SysBase->TDNestCnt=old_TDNestCnt;
  95     }
  96     /* Get active signals. */
  97     rcvd=me->tc_SigRecvd&signalSet;
  98
  99     /* And clear them. */
 100     me->tc_SigRecvd&=~signalSet;
 101
 102     /* All done. */
 103     Enable();
 104
 105     return rcvd;
 106     AROS_LIBFUNC_EXIT
 107 } /* Wait() */
 108