Re: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable & enable from context tracking on syscall entry

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> > > We cannot take the lock_trace(task) from irq context, and we 
> > > probably do not need to anyway, since we do not care about a 
> > > precise stack trace for the task.
> > 
> > So one worry with this and similar approaches of statistically 
> > detecting user mode would be the fact that on the way out to 
> > user-space we don't really destroy the previous call trace - we 
> > just pop off the stack (non-destructively), restore RIPs and are 
> > gone.
> > 
> > We'll need that percpu flag I suspect.
> 
> Note we have the context tracking state which tells where the 
> current task is: user/system/guest.

Yes, but that overhead is what I'm suggesting we get rid of, I thought 
Rik was trying to find a mechanism that would be independent of that?

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/