rom/exec/permit.c

   1 /*
   2     Copyright © 1995-2010, 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
  27     NAME */
  28
  29         AROS_LH0(void, Permit,
  30
  31 /*  LOCATION */
  32         struct ExecBase *, SysBase, 23, Exec)
  33
  34 /*  FUNCTION
  35         This function will reactivate the task dispatcher after a call
  36         to Forbid(). Note that calls to Forbid() nest, and for every
  37         call to Forbid() you need a matching call to Permit().
  38
  39     INPUTS
  40         None.
  41
  42     RESULT
  43         Multitasking will be re-enabled.
  44
  45     NOTES
  46         This function preserves all registers.
  47
  48         To prevent deadlocks calling Wait() in forbidden state breaks
  49         the forbid - thus taskswitches may happen again.
  50
  51     EXAMPLE
  52         No you really don't want to use this function.
  53
  54 BUGS
  55     The only architecture that you can rely on the registers being
  56     saved is on the Motorola mc68000 family.
  57
  58 SEE ALSO
  59     Forbid(), Disable(), Enable(), Wait()
  60
  61 INTERNALS
  62     If you want to preserve all the registers, replace this function
  63     in your $(KERNEL) directory. Otherwise this function is
  64     satisfactory.
  65
  66 HISTORY
  67
  68 ******************************************************************************/
  69 #undef Exec
  70 {
  71     AROS_LIBFUNC_INIT
  72
  73     /*
  74         Task switches are allowed again, if a switch is pending, we
  75         should allow it.
  76      */
  77
  78     AROS_ATOMIC_DEC(SysBase->TDNestCnt);
  79
  80     if(    ( SysBase->TDNestCnt < 0 )
  81         && ( SysBase->IDNestCnt < 0 )
  82         && ( SysBase->AttnResched & 0x80 ) )
  83     {
  84         /* Haha, you re-enabled multitasking, only to have the rug
  85            pulled out from under you feet :)
  86
  87            Clear the Switch() pending flag.
  88          */
  89
  90         if (KernelBase && !KrnIsSuper()) KrnSchedule();
  91     }
  92
  93     AROS_LIBFUNC_EXIT
  94 } /* Permit() */