arch/.unmaintained/ppc-native/exec/forbid.s

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 /*****************************************************************************
   7
   8     NAME
   9
  10         AROS_LH0(void, Forbid,
  11
  12     LOCATION
  13         struct ExecBase *, SysBase, 22, Exec)
  14
  15     FUNCTION
  16         Forbid any further taskswitches until a matching call to Permit().
  17         Naturally disabling taskswitches means:
  18
  19         THIS CALL IS DANGEROUS
  20
  21         Do not use it without thinking very well about it or better do not use
  22         it at all. Most of the time you can live without it by using semaphores
  23         or similar.
  24
  25         Calls to Forbid() nest, i.e. for each call to Forbid() you need one
  26         call to Enable().
  27
  28     INPUTS
  29
  30     RESULT
  31
  32     NOTES
  33         This function preserves all registers.
  34
  35         To prevent deadlocks calling Wait() in forbidden state breaks the
  36         firbid - thus taskswitches may happen again.
  37
  38     EXAMPLE
  39
  40     BUGS
  41
  42     SEE ALSO
  43         Permit(), Disable(), Enable(), Wait()
  44
  45     INTERNALS
  46
  47     HISTORY
  48
  49 ******************************************************************************/
  50
  51         #include "machine.i"
  52
  53         .text
  54         .balign 4
  55         .globl  AROS_SLIB_ENTRY(Forbid,Exec)
  56         .type   AROS_SLIB_ENTRY(Forbid,Exec),@function
  57 AROS_SLIB_ENTRY(Forbid,Exec):
  58         /* increment nesting count and return
  59            this seems to be a very unspectacular call and a good job for a C
  60            routine - but nothing in C can guarantee to preserve all registers
  61            and to increment atomically - so better use this simple assembly
  62            routine
  63         */
  64         subr
  65         push    scr
  66
  67         lbz     scr,TDNestCnt(base)
  68         addi    scr,scr,1
  69         stb     scr,TDNestCnt(base)
  70
  71         pop     scr
  72         rts
  73
  74