Messages in this thread | | | Date | Thu, 7 Jun 2007 19:28:07 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] enable interrupts in user path of page fault. |
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On Thu, 7 Jun 2007, Andrew Morton wrote: > > Interrupts got disabled here because do_page_fault() is an > interrupt-disabling trap, yes?
Yes - and it has to be: we want to disable preemption and interrupts that can fault on the vmalloc space, until we've at least saved away %cr2. We had bugs in that area before.
> The patch looks reasonable to me: a slight reduction in interrupt-off > latency when really weird things are happening.
I applied it as obviously correct.
> The patch also breaks things, I think: if userspace is running with > interrupts disabled and tries to access kernel memory it will presently > whizz through the kernel without ever enabling interrupts. With this > change, the kernel will now enable interrupts, which is presumably not what > the application wanted.
Well, we *do* enable interrupts for real page faults anyway, and this whole code just triggers for the case where we'd send a SIGSEGV. If some silly app really thought it could do that with interrupts disabled, it was wrong before too (we'd hit a reschedule point and enable them there anyway).
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