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Subject: Re: [PATCH v3 3/3] printk: use the lockless ringbuffer
To:     Petr Mladek <pmladek@suse.com>
Cc:     John Ogness <john.ogness@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrea Parri <parri.andrea@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Paul McKenney <paulmck@kernel.org>, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <20200618144919.9806-1-john.ogness@linutronix.de>
 <20200618144919.9806-4-john.ogness@linutronix.de>
 <ba338fab-9e98-366b-8fd4-05d4daa14f6d@redhat.com>
 <87zh8imgs5.fsf@jogness.linutronix.de>
 <585a6a1b-931c-1034-e2cc-da2c4381751e@redhat.com>
 <20200702133110.GE14288@alley>
From:   lijiang <lijiang@redhat.com>
Message-ID: <56266e04-56b2-41fa-fff1-c3437ddec929@redhat.com>
Date:   Sat, 4 Jul 2020 09:12:06 +0800
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在 2020年07月02日 21:31, Petr Mladek 写道:
> On Thu 2020-07-02 17:43:22, lijiang wrote:
>> 在 2020年07月02日 17:02, John Ogness 写道:
>>> On 2020-07-02, lijiang <lijiang@redhat.com> wrote:
>>>> About the VMCOREINFO part, I made some tests based on the kernel patch
>>>> v3, the makedumpfile and crash-utility can work as expected with your
>>>> patch(userspace patch), but, unfortunately, the vmcore-dmesg(kexec-tools)
>>>> can't correctly read the printk ring buffer information, and get the
>>>> following error:
>>>>
>>>> "Missing the log_buf symbol"
>>>>
>>>> The kexec-tools(vmcore-dmesg) should also have a similar patch, just like
>>>> in the makedumpfile and crash-utility.
>>>
>>> Yes, a patch for this is needed (as well as for any other related
>>> software floating around the internet).
>>>
>>> I have no RFC patches for vmcore-dmesg. Looking at the code, I think it
>>> would be quite straight forward to port the makedumpfile patch. I will
>>
>> Yes, it should be a similar patch.
>>
>>> try to make some time for this.
>>>
>> That would be nice. Thank you, John Ogness.
>>
>>> I do not want to patch any other software for this. I think with 3
>>> examples (crash, makedumpfile, vmcore-dmesg), others should be able to
>>
>> It's good enough to have the patch for the makedumpfile, crash and vmcore-dmesg,
>> which can ensure the kdump(userspace) work well.
> 
> I agree that this three are the most important ones and should be
> enough.
> 
> Thanks a lot for working on it and testing it.
> 
My pleasure. I will test the vmcore-dmesg later.

Thanks.
Lianbo

> Best Regards,
> Petr
>