arch/i386-pc/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 <asm/segments.h>
  15 #include <proto/exec.h>
  16
  17 void Exec_Permit_Supervisor();
  18
  19 /*****************************************************************************/
  20 #undef Exec
  21 #ifdef UseExecstubs
  22 #    define Exec _Exec
  23 #endif
  24
  25 /*  NAME */
  26
  27         AROS_LH0(void, Permit,
  28
  29 /*  LOCATION */
  30         struct ExecBase *, SysBase, 23, Exec)
  31
  32 /*  FUNCTION
  33         This function will reactivate the task dispatcher after a call
  34         to Forbid(). Note that calls to Forbid() nest, and for every
  35         call to Forbid() you need a matching call to Permit().
  36
  37     INPUTS
  38         None.
  39
  40     RESULT
  41         Multitasking will be re-enabled.
  42
  43     NOTES
  44         This function preserves all registers.
  45
  46         To prevent deadlocks, calling Wait() in forbidden state breaks
  47         the forbid - thus taskswitches may happen again.
  48
  49     EXAMPLE
  50         No you really don't want to use this function.
  51
  52     BUGS
  53         The only architecture that you can rely on the registers being
  54         saved is on the Motorola mc68000 family.
  55
  56     SEE ALSO
  57         Forbid(), Disable(), Enable(), Wait()
  58
  59     INTERNALS
  60         If you want to preserve all the registers, replace this function
  61         in your $(KERNEL) directory. Otherwise this function is
  62         satisfactory.
  63
  64     HISTORY
  65
  66 ******************************************************************************/
  67 #undef Exec
  68 {
  69     AROS_LIBFUNC_INIT
  70
  71     /*
  72         Task switches are allowed again, if a switch is pending, we
  73         should allow it.
  74     */
  75
  76     AROS_ATOMIC_DEC(SysBase->TDNestCnt);
  77
  78     if(    ( SysBase->TDNestCnt < 0 )
  79         && ( SysBase->IDNestCnt < 0 )
  80         && ( SysBase->AttnResched & 0x80 ) )
  81     {
  82         /* Haha, you re-enabled multitasking, only to have the rug
  83            pulled out from under you feet :)
  84
  85             Clear the Switch() pending flag.
  86         */
  87
  88         if (IN_USER_MODE) Supervisor((ULONG_FUNC)Exec_Permit_Supervisor);
  89     }
  90
  91     AROS_LIBFUNC_EXIT
  92 } /* Permit() */