linux-kernel - Re: [PATCH v3 3/3] printk: use the lockless ringbuffer

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Date:   Thu, 2 Jul 2020 15:31:10 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     lijiang <lijiang@...hat.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <parri.andrea@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...nel.org>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] printk: use the lockless ringbuffer

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@...hat.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.

Best Regards,
Petr