Re: frequent lockups in 3.18rc4

From: Linus Torvalds
Date: Fri Nov 21 2014 - 13:24:43 EST

On Fri, Nov 21, 2014 at 9:34 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> I see. You have issues with the use of current->active_mm instead of
> just doing a read_cr3() (and I'm sure other things).

Yes. And I have this memory of it actually mattering, where we'd get
get the page fault, but see that the (wrong) page table is already
populated, and say "ti wasn't a vmalloc fault", and then go down the
oops path.

Of course, the context switch itself has changed completely over the
years, but I think it would still be true with NMI. "active_mm" may
point to a different page table than the one the CPU is actually
using, and then the whole thing is bogus.

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