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