rom/exec/enable.c

   1 /*
   2     Copyright © 1995-2015, 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 #define DEBUG 0
  10
  11 #include <exec/execbase.h>
  12 #include <aros/libcall.h>
  13 #include <aros/atomic.h>
  14 #include <proto/kernel.h>
  15
  16 #include "exec_intern.h"
  17
  18 /*****************************************************************************/
  19 #undef  Exec
  20 #ifdef UseExecstubs
  21 #    define Exec _Exec
  22 #endif
  23
  24 /*  NAME */
  25 #include <proto/exec.h>
  26
  27         AROS_LH0(void, Enable,
  28
  29 /*  LOCATION */
  30         struct ExecBase *, SysBase, 21, Exec)
  31
  32 /*  FUNCTION
  33         This function will allow interrupts to occur after they have
  34         been disabled by Disable().
  35
  36         Note that calls to Disable() nest, and for every call to
  37         Disable() you need a matching call to Enable().
  38
  39         ***** WARNING *****
  40
  41         Using this function is considered very harmful, and it is
  42         not recommended to use this function for ** ANY ** reason.
  43
  44         It is quite possible to either crash the system, or to prevent
  45         normal activities (disk/port i/o) from occuring.
  46
  47         Note: As taskswitching is driven by the interrupts subsystem,
  48               this function has the side effect of disabling
  49               multitasking.
  50
  51     INPUTS
  52         None.
  53
  54     RESULT
  55         Interrupts will be enabled again when this call returns.
  56
  57     NOTES
  58         This function preserves all registers.
  59
  60         To prevent deadlocks calling Wait() in disabled state breaks
  61         the disable - thus interrupts may happen again.
  62
  63     EXAMPLE
  64         No you DEFINITATELY don't want to use this function.
  65
  66     BUGS
  67         The only architecture that you can rely on the registers being
  68         saved is on the Motorola mc68000 family.
  69
  70     SEE ALSO
  71         Forbid(), Permit(), Disable(), Wait()
  72
  73     INTERNALS
  74
  75 ******************************************************************************/
  76 {
  77 #undef Exec
  78
  79     AROS_LIBFUNC_INIT
  80
  81     D(bug("[Exec] Enable()\n");)
  82
  83     IDNESTCOUNT_DEC;
  84
  85     D(bug("[Exec] Enable: IDNESTCOUNT = %d\n", IDNESTCOUNT_GET);)
  86
  87     if (KernelBase)
  88     {
  89         if (IDNESTCOUNT_GET < 0)
  90         {
  91             D(bug("[Exec] Enable: Enabling interrupts\n");)
  92
  93             KrnSti();
  94
  95             /* The following stuff is not safe to call from within supervisor mode */
  96             if (!KrnIsSuper())
  97             {
  98                 /*
  99                  * There's no dff09c like thing in x86 native which would allow
 100                  * us to set delayed (mark it as pending but it gets triggered
 101                  * only once interrupts are enabled again) software interrupt,
 102                  * so we check it manually here in Enable(), similar to Permit().
 103                  */
 104                 if (SysBase->SysFlags & SFF_SoftInt)
 105                 {
 106                     /*
 107                      * First we react on SFF_SoftInt by issuing KrnCause() call. This triggers
 108                      * the complete interrupt processing code in kernel, which implies also
 109                      * rescheduling if became necessary.
 110                      */
 111                     D(bug("[Exec] Enable: causing softints\n");)
 112                     KrnCause();
 113                 }
 114
 115                 if ((TDNESTCOUNT_GET < 0) && FLAG_SCHEDSWITCH_ISSET)
 116                 {
 117                     /*
 118                      * If SFF_SoftInt hasn't been set, we have a chance that task switching
 119                      * is enabled and pending. We need to trigger it here in such a case.
 120                      */
 121                     D(bug("[Exec] Enable: rescheduling\n");)
 122                     KrnSchedule();
 123                 }
 124             }
 125         }
 126     }
 127
 128     AROS_LIBFUNC_EXIT
 129 } /* Enable() */