arch/ppc-chrp/exec/permit.c

   1 /*
   2     Copyright © 1995-2001, 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 extern void *priv_KernelBase;
  18
  19 #undef Exec
  20 #ifdef UseExecstubs
  21 #    define Exec _Exec
  22 #endif
  23
  24 /*  NAME */
  25
  26         AROS_LH0(void, Permit,
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 23, Exec)
  30
  31 /*  FUNCTION
  32         This function will reactivate the task dispatcher after a call
  33         to Forbid(). Note that calls to Forbid() nest, and for every
  34         call to Forbid() you need a matching call to Permit().
  35
  36     INPUTS
  37         None.
  38
  39     RESULT
  40         Multitasking will be re-enabled.
  41
  42     NOTES
  43         This function preserves all registers.
  44
  45         To prevent deadlocks calling Wait() in forbidden state breaks
  46         the forbid - thus taskswitches may happen again.
  47
  48     EXAMPLE
  49         No you really don't want to use this function.
  50
  51 BUGS
  52     The only architecture that you can rely on the registers being
  53     saved is on the Motorola mc68000 family.
  54
  55 SEE ALSO
  56     Forbid(), Disable(), Enable(), Wait()
  57
  58 INTERNALS
  59     If you want to preserve all the registers, replace this function
  60     in your $(KERNEL) directory. Otherwise this function is
  61     satisfactory.
  62
  63 HISTORY
  64
  65 ******************************************************************************/
  66 #undef Exec
  67 {
  68     AROS_LIBFUNC_INIT
  69
  70     void *KernelBase = priv_KernelBase;
  71
  72     /*
  73         Task switches are allowed again, if a switch is pending, we
  74         should allow it.
  75      */
  76
  77     AROS_ATOMIC_DEC(SysBase->TDNestCnt);
  78
  79     if(    ( SysBase->TDNestCnt < 0 )
  80         && ( SysBase->IDNestCnt < 0 )
  81         && ( SysBase->AttnResched & 0x80 ) )
  82     {
  83         /* Haha, you re-enabled multitasking, only to have the rug
  84            pulled out from under you feet :)
  85
  86            Clear the Switch() pending flag.
  87          */
  88
  89         if (KernelBase && !KrnIsSuper())
  90                 KrnSchedule();
  91     }
  92
  93     AROS_LIBFUNC_EXIT
  94 } /* Permit() */