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