Interrupt disabling design

Interrupt disabling design

[Garcia Jérémie]

Hi everybody,=20
I'm trying to emulate a VxWorks-designed application under a linux =
montavista environment.
In this application I have critical portion of code which need the =
interrupts disabled as below:

-------------------------------------
  lockKey =3D OSIntrLock();some=20
    .
    . // my critical code =20
    .
  bsos1IntrUnlock(lockKey);
-------------------------------------
As you can see we use an OS encapsulation layer which is used to call =
the OS routines:

----------------------------
int OSIntrLock(void)
{
  return (intLock());  // vxWorks routine
}

void OSIntrUnlock(int lockKey)
{
  intUnlock(lockKey);  // vxWorks routine
}
----------------------------

Furthermore, I'm running my "VxWorks emulator" in the user-space and I'm =
not allowed to modify files others than the OS encapsulation layer ones.
So, how can I use the "cli() / sti()" functions from the user space as =
below:


 | USER-SPACE   |  --> | KERNEL-SPACE |  --> |    USER-SPACE    | --> | =
KERNEL-SPACE |  --> | USER-SPACE |
 |              |      |              |      |                  |     |  =
            |      |            |        =20
 | OSIntrLock() |      |   cli()      |      | my critical code |     |  =
  sti()     |      |   .....    |
                                             |  OSIntrUnlock()  |   =20

Is it possible to do that? Cause If I do a "cli()" call, I disable =
interrupts --> so, will the "sti()" call work?
If yes, it allows me to make my own system call to use them from the =
user space but I'm not really sure...

Tks a lot for your help=20

Re: Interrupt disabling design

[Pantelis Antoniou]

Garcia Jérémie wrote:
> Hi everybody, 
> I'm trying to emulate a VxWorks-designed application under a linux montavista environment.
> In this application I have critical portion of code which need the interrupts disabled as below:

[snip]
> 
> Is it possible to do that? Cause If I do a "cli()" call, I disable interrupts --> so, will the "sti()" call work?
> If yes, it allows me to make my own system call to use them from the user space but I'm not really sure...
> 
> Tks a lot for your help 
> _______________________________________________

Although it might be possible to something like that with root permissions,
  I'd recommend against it.

If you want to run code with disabled interrupts, move that code in a kernel
module and disable/enable interrupts in the kernel
(still bad but acceptable).

IMHO of course.

Regards

Pantelis

Re: Interrupt disabling design

[Benjamin Herrenschmidt]

On Thu, 2005-04-07 at 12:23 +0200, Garcia Jérémie wrote:
> Hi everybody, 
> I'm trying to emulate a VxWorks-designed application under a linux montavista environment.
> In this application I have critical portion of code which need the interrupts disabled as below:
> 
> -------------------------------------
>   lockKey = OSIntrLock();some 
>     .
>     . // my critical code  
>     .
>   bsos1IntrUnlock(lockKey);
> -------------------------------------
> As you can see we use an OS encapsulation layer which is used to call the OS routines:

On Linux, you can disable interrupts only on the current CPU. If your HW
is SMP, that cannot work, you need to complement the interrupt disabling
with a spinlock.

> ----------------------------
> int OSIntrLock(void)
> {
>   return (intLock());  // vxWorks routine
> }
> 
> void OSIntrUnlock(int lockKey)
> {
>   intUnlock(lockKey);  // vxWorks routine
> }
> ----------------------------
> 
> Furthermore, I'm running my "VxWorks emulator" in the user-space and I'm not allowed to modify files others than the OS encapsulation layer ones.
> So, how can I use the "cli() / sti()" functions from the user space as below:

You cannot. Never. Forget it. If you ever need to actually disable
interrupts, you have to be a kernel driver. Period. Wrong model.

> 
>  | USER-SPACE   |  --> | KERNEL-SPACE |  --> |    USER-SPACE    | --> | KERNEL-SPACE |  --> | USER-SPACE |
>  |              |      |              |      |                  |     |              |      |            |         
>  | OSIntrLock() |      |   cli()      |      | my critical code |     |    sti()     |      |   .....    |
>                                              |  OSIntrUnlock()  |    
> 
> Is it possible to do that? Cause If I do a "cli()" call, I disable interrupts --> so, will the "sti()" call work?
> If yes, it allows me to make my own system call to use them from the user space but I'm not really sure...
> 
> Tks a lot for your help 
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
-- 
Benjamin Herrenschmidt <benh@kernel.crashing.org>