rom/exec/permit.c

   1 /*
   2     Copyright © 1995-2015, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Permit() - Allow tasks switches to occur.
   6     Lang: english
   7 */
   8
   9 #define DEBUG 0
  10
  11 #include <exec/types.h>
  12 #include <exec/execbase.h>
  13 #include <aros/libcall.h>
  14 #include <aros/atomic.h>
  15 #include <aros/debug.h>
  16 #include <proto/exec.h>
  17 #include <proto/kernel.h>
  18
  19 #include "exec_intern.h"
  20
  21 #undef Exec
  22 #ifdef UseExecstubs
  23 #    define Exec _Exec
  24 #endif
  25
  26 /*****************************************************************************
  27
  28     NAME */
  29
  30         AROS_LH0(void, Permit,
  31
  32 /*  LOCATION */
  33         struct ExecBase *, SysBase, 23, Exec)
  34
  35 /*  FUNCTION
  36         This function will reactivate the task dispatcher after a call
  37         to Forbid(). Note that calls to Forbid() nest, and for every
  38         call to Forbid() you need a matching call to Permit().
  39
  40     INPUTS
  41         None.
  42
  43     RESULT
  44         Multitasking will be re-enabled.
  45
  46     NOTES
  47         This function preserves all registers.
  48
  49         To prevent deadlocks calling Wait() in forbidden state breaks
  50         the forbid - thus taskswitches may happen again.
  51
  52     EXAMPLE
  53         No you really don't want to use this function.
  54
  55     BUGS
  56         The only architecture that you can rely on the registers being
  57         saved is on the Motorola mc68000 family.
  58
  59     SEE ALSO
  60         Forbid(), Disable(), Enable(), Wait()
  61
  62     INTERNALS
  63         If you want to preserve all the registers, replace this function
  64         in your $(KERNEL) directory. Otherwise this function is
  65         satisfactory.
  66
  67     HISTORY
  68
  69
  70 ******************************************************************************/
  71 #undef Exec
  72 {
  73     AROS_LIBFUNC_INIT
  74
  75     D(bug("[Exec] Permit()\n"));
  76
  77     /*
  78      * Task switches are allowed again, if a switch is pending, we
  79      * should allow it.
  80      */
  81     TDNESTCOUNT_DEC;
  82
  83     D(bug("[Exec] Permit: TDNESTCOUNT = %d\n", TDNESTCOUNT_GET));
  84
  85     if (KernelBase && !KrnIsSuper())
  86     {
  87         if(    ( TDNESTCOUNT_GET < 0 )
  88             && ( IDNESTCOUNT_GET < 0 )
  89             && ( FLAG_SCHEDSWITCH_ISSET ) )
  90         {
  91             /*
  92              * Haha, you re-enabled multitasking, only to have the rug
  93              * pulled out from under you feet :)
  94
  95              * Clear the Switch() pending flag.
  96              */
  97             D(bug("[Exec] Permit: rescheduling\n"));
  98             KrnSchedule();
  99         }
 100     }
 101
 102     AROS_LIBFUNC_EXIT
 103 } /* Permit() */