rom/exec/enable.c

   1 /*
   2     Copyright © 1995-2010, 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/types.h>
  10 #include <exec/execbase.h>
  11 #include <aros/libcall.h>
  12 #include <aros/atomic.h>
  13 #include <proto/kernel.h>
  14
  15 #include "exec_intern.h"
  16
  17 /*****************************************************************************/
  18 #undef  Exec
  19 #ifdef UseExecstubs
  20 #    define Exec _Exec
  21 #endif
  22
  23 /*  NAME */
  24 #include <proto/exec.h>
  25
  26         AROS_LH0(void, Enable,
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 21, Exec)
  30
  31 /*  FUNCTION
  32         This function will allow interrupts to occur after they have
  33         been disabled by Disable().
  34
  35         Note that calls to Disable() nest, and for every call to
  36         Disable() you need a matching call to Enable().
  37
  38         ***** WARNING *****
  39
  40         Using this function is considered very harmful, and it is
  41         not recommended to use this function for ** ANY ** reason.
  42
  43         It is quite possible to either crash the system, or to prevent
  44         normal activities (disk/port i/o) from occuring.
  45
  46         Note: As taskswitching is driven by the interrupts subsystem,
  47               this function has the side effect of disabling
  48               multitasking.
  49
  50     INPUTS
  51         None.
  52
  53     RESULT
  54         Interrupts will be enabled again when this call returns.
  55
  56     NOTES
  57         This function preserves all registers.
  58
  59         To prevent deadlocks calling Wait() in disabled state breaks
  60         the disable - thus interrupts may happen again.
  61
  62     EXAMPLE
  63         No you DEFINITATELY don't want to use this function.
  64
  65     BUGS
  66         The only architecture that you can rely on the registers being
  67         saved is on the Motorola mc68000 family.
  68
  69     SEE ALSO
  70         Forbid(), Permit(), Disable(), Wait()
  71
  72     INTERNALS
  73         This function must be replaced in the $(KERNEL) or $(ARCH)
  74         directories in order to do some work.
  75
  76 ******************************************************************************/
  77 {
  78 #undef Exec
  79
  80     AROS_LIBFUNC_INIT
  81
  82 #ifdef AROS_NO_ATOMIC_OPERATIONS
  83     SysBase->IDNestCnt--;
  84 #else
  85     AROS_ATOMIC_DEC(SysBase->IDNestCnt);
  86 #endif
  87
  88     if (KernelBase && (SysBase->IDNestCnt < 0))
  89     {
  90         D(bug("[Enable] Enabling interrupts\n"));
  91         KrnSti();
  92
  93         if (KrnIsSuper())
  94             return;
  95
  96         /* There's no dff09c like thing in x86 native which would allow
  97            us to set delayed (mark it as pending but it gets triggered
  98            only once interrupts are enabled again) software interrupt,
  99            so we check it manually here in Enable() == same stuff as
 100            in Permit(). */
 101
 102         if ((SysBase->TDNestCnt < 0) && (SysBase->AttnResched & ARF_AttnSwitch))
 103         {
 104             KrnSchedule();
 105         }
 106
 107         if (SysBase->SysFlags & SFF_SoftInt)
 108             KrnCause();
 109     }
 110
 111     AROS_LIBFUNC_EXIT
 112 } /* Enable() */