rom/exec/enable.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Enable() - Allow interrupts to occur after Disable().
   6     Lang: english
   7 */
   8
   9 #include <exec/execbase.h>
  10 #include <aros/libcall.h>
  11 #include <aros/atomic.h>
  12 #include <proto/kernel.h>
  13
  14 #include "exec_intern.h"
  15
  16 /*****************************************************************************/
  17 #undef  Exec
  18 #ifdef UseExecstubs
  19 #    define Exec _Exec
  20 #endif
  21
  22 /*  NAME */
  23 #include <proto/exec.h>
  24
  25         AROS_LH0(void, Enable,
  26
  27 /*  LOCATION */
  28         struct ExecBase *, SysBase, 21, Exec)
  29
  30 /*  FUNCTION
  31         This function will allow interrupts to occur after they have
  32         been disabled by Disable().
  33
  34         Note that calls to Disable() nest, and for every call to
  35         Disable() you need a matching call to Enable().
  36
  37         ***** WARNING *****
  38
  39         Using this function is considered very harmful, and it is
  40         not recommended to use this function for ** ANY ** reason.
  41
  42         It is quite possible to either crash the system, or to prevent
  43         normal activities (disk/port i/o) from occuring.
  44
  45         Note: As taskswitching is driven by the interrupts subsystem,
  46               this function has the side effect of disabling
  47               multitasking.
  48
  49     INPUTS
  50         None.
  51
  52     RESULT
  53         Interrupts will be enabled again when this call returns.
  54
  55     NOTES
  56         This function preserves all registers.
  57
  58         To prevent deadlocks calling Wait() in disabled state breaks
  59         the disable - thus interrupts may happen again.
  60
  61     EXAMPLE
  62         No you DEFINITATELY don't want to use this function.
  63
  64     BUGS
  65         The only architecture that you can rely on the registers being
  66         saved is on the Motorola mc68000 family.
  67
  68     SEE ALSO
  69         Forbid(), Permit(), Disable(), Wait()
  70
  71     INTERNALS
  72
  73 ******************************************************************************/
  74 {
  75 #undef Exec
  76
  77     AROS_LIBFUNC_INIT
  78
  79 #ifdef AROS_NO_ATOMIC_OPERATIONS
  80     SysBase->IDNestCnt--;
  81 #else
  82     AROS_ATOMIC_DEC(SysBase->IDNestCnt);
  83 #endif
  84
  85     if (KernelBase && (SysBase->IDNestCnt < 0))
  86     {
  87         D(bug("[Enable] Enabling interrupts\n"));
  88         KrnSti();
  89
  90         if (KrnIsSuper())
  91         {
  92             /* The following stuff is not safe to call from within supervisor mode */
  93             return;
  94         }
  95
  96         /*
  97          * There's no dff09c like thing in x86 native which would allow
  98          * us to set delayed (mark it as pending but it gets triggered
  99          * only once interrupts are enabled again) software interrupt,
 100          * so we check it manually here in Enable(), similar to Permit().
 101          */
 102         if (SysBase->SysFlags & SFF_SoftInt)
 103         {
 104             /*
 105              * First we react on SFF_SoftInt by issuing KrnCause() call. This triggers
 106              * the complete interrupt processing code in kernel, which implies also
 107              * rescheduling if became necessary.
 108              */
 109             KrnCause();
 110         }
 111
 112         if ((SysBase->TDNestCnt < 0) && (SysBase->AttnResched & ARF_AttnSwitch))
 113         {
 114             /*
 115              * If SFF_SoftInt hasn't been set, we have a chance that task switching
 116              * is enabled and pending. We need to trigger it here in such a case.
 117              */
 118             KrnSchedule();
 119         }
 120     }
 121
 122     AROS_LIBFUNC_EXIT
 123 } /* Enable() */