rom/exec/forbid.c

   1 /*
   2     Copyright © 1995-2015, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Forbid() - Prevent tasks switches from taking place.
   6     Lang: english
   7 */
   8
   9 #define DEBUG 0
  10
  11 #include <exec/types.h>
  12 #include <exec/execbase.h>
  13 #include <aros/libcall.h>
  14 #include <aros/atomic.h>
  15
  16 #include "exec_intern.h"
  17
  18 #undef Exec
  19 #ifdef UseExecstubs
  20 #    define Exec _Exec
  21 #endif
  22
  23 /*****************************************************************************/
  24
  25
  26 /*  NAME */
  27 #include <proto/exec.h>
  28
  29         AROS_LH0(void, Forbid,
  30
  31 /*  LOCATION */
  32         struct ExecBase *, SysBase, 22, Exec)
  33
  34 /*  FUNCTION
  35         Forbid any further taskswitches until a matching call to Permit().
  36         Naturally disabling taskswitches means:
  37
  38         THIS CALL IS DANGEROUS
  39
  40         Do not use it without thinking very well about it or better
  41         do not use it at all. Most of the time you can live without
  42         it by using semaphores or similar.
  43
  44         Calls to Forbid() nest, i.e. for each call to Forbid() you
  45         need one call to Permit().
  46
  47     INPUTS
  48         None.
  49
  50     RESULT
  51         The multitasking state will be disabled AFTER this function
  52         returns to the caller.
  53
  54     NOTES
  55         This function preserves all registers.
  56
  57         To prevent deadlocks calling Wait() in forbidden state breaks
  58         the forbid - thus taskswitches may happen again.
  59
  60     EXAMPLE
  61         No you really don't want to use this function.
  62
  63     BUGS
  64         The only architecture that you can rely on the registers being
  65         saved is on the Motorola mc68000 family.
  66
  67     SEE ALSO
  68         Permit(), Disable(), Enable(), Wait()
  69
  70     INTERNALS
  71         If you want to preserve all the registers, replace this function
  72         in your $(KERNEL) directory. Otherwise this function is
  73         satisfactory.
  74
  75 ******************************************************************************/
  76 {
  77 #undef Exec
  78
  79     AROS_LIBFUNC_INIT
  80
  81     D(bug("[Exec] Forbid()\n"));
  82
  83     TDNESTCOUNT_INC;
  84
  85     D(bug("[Exec] Forbid: TDNESTCOUNT = %d\n", TDNESTCOUNT_GET);)
  86
  87     AROS_LIBFUNC_EXIT
  88 } /* Forbid() */