linux-kernel - Re: [PATCH v8 13/19] locking/rwsem: Make rwsem->owner an atomic_long

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Date:   Sun, 21 Jul 2019 21:49:50 +0100
From:   Luis Henriques <lhenriques@...e.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Borislav Petkov <bp@...en8.de>,
        Will Deacon <will.deacon@....com>,
        "huang ying" <huang.ying.caritas@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jeff Layton <jlayton@...nel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Linux List Kernel Mailing" <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v8 13/19] locking/rwsem: Make rwsem->owner an atomic_long_t

Waiman Long <longman@...hat.com> writes:

> On 7/20/19 4:41 AM, Luis Henriques wrote:
>> "Linus Torvalds" <torvalds@...ux-foundation.org> writes:
>>
>>> On Fri, Jul 19, 2019 at 12:32 PM Waiman Long <longman@...hat.com> wrote:
>>>> This patch shouldn't change the behavior of the rwsem code. The code
>>>> only access data within the rw_semaphore structures. I don't know why it
>>>> will cause a KASAN error. I will have to reproduce it and figure out
>>>> exactly which statement is doing the invalid access.
>>> The stack traces should show line numbers if you run them through
>>> scripts/decode_stacktrace.sh.
>>>
>>> You need to have debug info enabled for that, though.
>>>
>>> Luis?
>>>
>>>              Linus
>> Yep, sure.  And I should have done this in the initial report.  It's a
>> different trace, I had to recompile the kernel.
>>
>> (I'm also adding Jeff to the CC list.)
>>
>> Cheers,
>
> Thanks for the information. I think I know where the problem is. Would
> you mind applying the attached patch to see if it can fix the KASAN error.

Yep, that seems to work -- I can't reproduce the error anymore (and
sorry for the delay).  Thanks!  And feel free to add my Tested-by.

Cheers,
-- 
Luis