[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <alpine.LFD.0.98.0706071925260.4205@woody.linux-foundation.org>
Date: Thu, 7 Jun 2007 19:28:07 -0700 (PDT)
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Christoph Hellwig <hch@...radead.org>, Andi Kleen <ak@...e.de>
Subject: Re: [PATCH] enable interrupts in user path of page fault.
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).
Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists