rom/exec/forbid.c

   1 /*
   2     Copyright © 1995-2001, 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 /*****************************************************************************/
  15 #undef  Exec
  16 #ifdef UseExecstubs
  17 #    define Exec _Exec
  18 #endif
  19
  20 /*  NAME */
  21 #include <proto/exec.h>
  22
  23         AROS_LH0(void, Forbid,
  24
  25 /*  LOCATION */
  26         struct ExecBase *, SysBase, 22, Exec)
  27
  28 /*  FUNCTION
  29         Forbid any further taskswitches until a matching call to Permit().
  30         Naturally disabling taskswitches means:
  31
  32         THIS CALL IS DANGEROUS
  33
  34         Do not use it without thinking very well about it or better
  35         do not use it at all. Most of the time you can live without
  36         it by using semaphores or similar.
  37
  38         Calls to Forbid() nest, i.e. for each call to Forbid() you
  39         need one call to Permit().
  40
  41     INPUTS
  42         None.
  43
  44     RESULT
  45         The multitasking state will be disabled AFTER this function
  46         returns to the caller.
  47
  48     NOTES
  49         This function preserves all registers.
  50
  51         To prevent deadlocks calling Wait() in forbidden state breaks
  52         the forbid - thus taskswitches may happen again.
  53
  54     EXAMPLE
  55         No you really don't want to use this function.
  56
  57     BUGS
  58         The only architecture that you can rely on the registers being
  59         saved is on the Motorola mc68000 family.
  60
  61     SEE ALSO
  62         Permit(), Disable(), Enable(), Wait()
  63
  64     INTERNALS
  65         If you want to preserve all the registers, replace this function
  66         in your $(KERNEL) directory. Otherwise this function is
  67         satisfactory.
  68
  69 ******************************************************************************/
  70 {
  71 #undef Exec
  72
  73     AROS_LIBFUNC_INIT
  74
  75     AROS_ATOMIC_INC(SysBase->TDNestCnt);
  76
  77     AROS_LIBFUNC_EXIT
  78 } /* Forbid() */