Messages in this thread | | | Date | Thu, 7 May 2015 14:29:13 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable & enable from context tracking on syscall entry |
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* Frederic Weisbecker <fweisbec@gmail.com> 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
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