Date: Wed, 9 Oct 2013 14:52:28 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>, Oleg Nesterov <oleg@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [x86] BUG: unable to handle kernel paging request at 00740060
Message-ID: <20131009125228.GA24215@gmail.com>
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 <20131008143400.GA14721@redhat.com>
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Oct 09, 2013 at 08:19:11PM +0800, Fengguang Wu wrote:
> > > > Fengguang, I do not think this will help, but just in case. Could you
> > > > show the result of
> > > > 
> > > >         $ kernel/task_work.s
> > 
> > Update: I recompiled the kernel with gcc 4.4.7 and find it booting fine!
> 
> > # 208 "/c/wfg/tip/arch/x86/include/asm/bitops.h" 1
> > 	bts $1, 8(%eax); setc %dl	#,, c
> 
> That compiler doesn't appear to have asm goto support, so we fall back
> to the code we already knew worked :-)

I'm using 4.7.2 with randconfig testing, which has asm goto support, and I 
haven't seen this crash yet.

Unless my testing is off it might be a bug in GCC 4.8, or a pre-existing 
bug gets exposed by GCC 4.8.

Thanks,

	Ingo
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