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From: Andy Lutomirski <luto@amacapital.net>
To: Waiman Long <waiman.long@hp.com>
Cc: Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Scott J Norton <scott.norton@hp.com>,
	Aswin Chandramouleeswaran <aswin@hp.com>,
	tip-bot for Peter Zijlstra <tipbot@zytor.com>,
	linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] x86, mm, perf: Allow recursive faults from interrupts
Date: Fri, 17 Jan 2014 13:07:20 -0800
Message-ID: <CALCETrXtCZG76xBx0WnNFkNWgSm2dB8FfB1iHP04yK3YwcH=kg@mail.gmail.com> (raw)
In-Reply-To: <52D98DAD.9090501@hp.com>

On Fri, Jan 17, 2014 at 12:08 PM, Waiman Long <waiman.long@hp.com> wrote:
> On 01/17/2014 02:17 PM, Andy Lutomirski wrote:
>>
>> On Fri, Jan 17, 2014 at 10:10 AM, Waiman Long<waiman.long@hp.com>  wrote:
>>>
>>> On 01/16/2014 08:39 AM, tip-bot for Peter Zijlstra wrote:
>>>>
>>>> Commit-ID:  c026b3591e4f2a4993df773183704bb31634e0bd
>>>> Gitweb:
>>>> http://git.kernel.org/tip/c026b3591e4f2a4993df773183704bb31634e0bd
>>>> Author:     Peter Zijlstra<peterz@infradead.org>
>>>> AuthorDate: Fri, 10 Jan 2014 21:06:03 +0100
>>>> Committer:  Ingo Molnar<mingo@kernel.org>
>>>> CommitDate: Thu, 16 Jan 2014 09:19:48 +0100
>>>>
>>>> x86, mm, perf: Allow recursive faults from interrupts
>>>>
>>>> Waiman managed to trigger a PMI while in a emulate_vsyscall() fault,
>>>> the PMI in turn managed to trigger a fault while obtaining a stack
>>>> trace. This triggered the sig_on_uaccess_error recursive fault logic
>>>> and killed the process dead.
>>>>
>>>> Fix this by explicitly excluding interrupts from the recursive fault
>>>> logic.
>>>>
>>>> Reported-and-Tested-by: Waiman Long<waiman.long@hp.com>
>>>> Fixes: e00b12e64be9 ("perf/x86: Further optimize copy_from_user_nmi()")
>>>> Cc: Aswin Chandramouleeswaran<aswin@hp.com>
>>>> Cc: Scott J Norton<scott.norton@hp.com>
>>>> Cc: Linus Torvalds<torvalds@linux-foundation.org>
>>>> Cc: Andy Lutomirski<luto@amacapital.net>
>>>> Cc: Arnaldo Carvalho de Melo<acme@ghostprotocols.net>
>>>> Cc: Andrew Morton<akpm@linux-foundation.org>
>>>> Signed-off-by: Peter Zijlstra<peterz@infradead.org>
>>>> Link:
>>>>
>>>> http://lkml.kernel.org/r/20140110200603.GJ7572@laptop.programming.kicks-ass.net
>>>> Signed-off-by: Ingo Molnar<mingo@kernel.org>
>>>> ---
>>>>    arch/x86/mm/fault.c | 18 ++++++++++++++++++
>>>>    1 file changed, 18 insertions(+)
>>>>
>>>>
>>> Will that be picked up by Linus as it is a 3.13 regression?
>>
>> Does anyone actually know why this regressed recently?  The buggy code
>> has been there for quite a while.
>>
>> --Andy
>
>
> Yes, the bug was there for a while, but a recent change by Peter (see the
> "Fixes:" line above) made it much easier to hit it.

Thanks!

So I feel slightly better now -- this particular bug didn't actually
exist when I wrote the offending code :)  But that also means that
this should really be fixed in 3.13.

--Andy

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-10 15:29 SIGSEGV when using "perf record -g" with 3.13-rc* kernel Waiman Long
2014-01-10 16:58 ` Peter Zijlstra
2014-01-10 17:02   ` Peter Zijlstra
2014-01-10 17:41     ` Peter Zijlstra
2014-01-10 18:54       ` Andy Lutomirski
2014-01-10 19:43         ` Waiman Long
2014-01-10 19:56           ` Andy Lutomirski
2014-01-10 20:12             ` Peter Zijlstra
2014-01-10 20:06         ` Peter Zijlstra
2014-01-10 20:28           ` Andy Lutomirski
2014-01-15 15:33           ` Waiman Long
2014-01-16 13:39           ` [tip:perf/core] x86, mm, perf: Allow recursive faults from interrupts tip-bot for Peter Zijlstra
2014-01-17 18:10             ` Waiman Long
2014-01-17 19:17               ` Andy Lutomirski
2014-01-17 20:08                 ` Waiman Long
2014-01-17 21:07                   ` Andy Lutomirski [this message]
2014-01-10 19:37     ` SIGSEGV when using "perf record -g" with 3.13-rc* kernel Waiman Long
2014-01-10 20:10       ` Peter Zijlstra

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