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