linux-kernel - Re: [x86] BUG: unable to handle kernel paging request at 00740060

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Date:	Tue, 8 Oct 2013 12:49:29 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Jakub Jelinek <jakub@...hat.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Richard Henderson <rth@...ddle.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [x86] BUG: unable to handle kernel paging request at 00740060

On Tue, Oct 8, 2013 at 12:35 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> Cough... sorry for off-topic question,
>
>         static inline int test_and_set_bit(long nr, volatile unsigned long *addr)
>         {
>                 int oldbit;
>
>                 asm volatile(LOCK_PREFIX "bts %2,%1\n\t"
>                              "sbb %0,%0" : "=r" (oldbit), ADDR : "Ir" (nr) : "memory");
>
> doesn't this mean that "ADDR" doesn't need "+" as well?

We use ADDR for some of the non-barrier ones too, that don't have the
barrier. See clear_bit() and friends..

> Or at least, perhaps it makes sense to identify the include file which
> makes the difference. Say, revert the changes in bitops.h, retest, then
> in atomic.h if the kernel still fails, etc.

Yeah, except Fengguang is the only one seeing this in his automated tests..

              Linus
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