rom/exec/disable.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Disable() - Stop interrupts from occurring.
   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, Disable,
  24
  25 /*  LOCATION */
  26         struct ExecBase *, SysBase, 20, Exec)
  27
  28 /*  FUNCTION
  29         This function will prevent interrupts from occuring. You can
  30         start the interrupts again with a call to Enable().
  31
  32         Note that calls to Disable() nest, and for every call to
  33         Disable() you need a matching call to Enable().
  34
  35         ***** WARNING *****
  36
  37         Using this function is considered very harmful, and it is
  38         not recommended to use this function for ** ANY ** reason.
  39
  40         It is quite possible to either crash the system, or to prevent
  41         normal activities (disk/port i/o) from occuring.
  42
  43         Note: As taskswitching is driven by the interrupts subsystem,
  44               this function has the side effect of disabling
  45               multitasking.
  46
  47     INPUTS
  48
  49     RESULT
  50         Interrupts will be disabled AFTER this call returns.
  51
  52     NOTES
  53         This function preserves all registers.
  54
  55         To prevent deadlocks calling Wait() in disabled state breaks
  56         the disable - thus interrupts may happen again.
  57
  58     EXAMPLE
  59         No you DEFINITELY 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         Forbid(), Permit(), Enable(), Wait()
  67
  68     INTERNALS
  69         This function must be replaced in the $(KERNEL) or $(ARCH)
  70         directories in order to do some work.
  71
  72 ******************************************************************************/
  73 {
  74 #undef Exec
  75
  76     AROS_LIBFUNC_INIT
  77
  78     /* Only disable interrupts if they are not already disabled. The
  79        initial (enabled) value of IDNestCnt is -1
  80     */
  81
  82     AROS_ATOMIC_INC(SysBase->IDNestCnt);
  83
  84     /*
  85         We have to disable interrupts, however some silly person
  86         hasn't written the code required to do it yet. They should
  87         have created a file in config/$(KERNEL)/exec or
  88         config/$(ARCH)/exec called disable.c or disable.s which
  89         implements this function.
  90     */
  91     #ifndef __CXREF__
  92     #error You have not written the $(KERNEL) interrupt subsystem!
  93     #endif
  94
  95     AROS_LIBFUNC_EXIT
  96 } /* Disable() */