linux-kernel - Re: [PATCH 0/2] printk: replace ringbuffer

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Date:   Wed, 5 Feb 2020 18:19:02 +0800
From:   lijiang <lijiang@...hat.com>
To:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] printk: replace ringbuffer

> On 2020-02-05, Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> wrote:
>>>>> So there is a General protection fault. That's the type of a
>>>>> problem that kills the boot for me as well (different backtrace,
>>>>> tho).
>>>>
>>>> Do you have CONFIG_RELOCATABLE and CONFIG_RANDOMIZE_BASE (KASLR)
>>>> enabled?
>>>
>>> Yes. These two options are enabled.
>>>
>>> CONFIG_RELOCATABLE=y
>>> CONFIG_RANDOMIZE_BASE=y
>>
>> So KASLR kills the boot for me. So does KASAN.
> 
> Sergey, thanks for looking into this already!
> 
>> John, do you see any of these problems on your test machine?
> 
> For x86 I have only been using qemu. (For hardware tests I use arm64-smp
> in order to verify memory barriers.) With qemu-x86_64 I am unable to
> reproduce the problem.
> 
> Lianbo, thanks for the report. Can you share your boot args? Anything
> special in there (like log_buf_len=, earlyprintk, etc)?
> 
Thanks for your response. Here is my kernel command line:

Command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.5.0-rc7+ root=/dev/mapper/intel--wildcatpass--07-root ro crashkernel=512M resume=/dev/mapper/intel--wildcatpass--07-swap rd.lvm.lv=intel-wildcatpass-07/root rd.lvm.lv=intel-wildcatpass-07/swap console=ttyS0,115200n81

BTW: Actually, I put the complete kernel log in my last email reply, you could check the attachment if needed.

> Also, could you share your CONFIG_LOG_* and CONFIG_PRINTK_* options?
> 
Sure. Please refer to it.

[root@...el-wildcatpass-07 linux]# grep -nr "CONFIG_LOG_" .config 
134:CONFIG_LOG_BUF_SHIFT=20
135:CONFIG_LOG_CPU_MAX_BUF_SHIFT=12

[root@...el-wildcatpass-07 linux]# grep -nr "CONFIG_PRINTK_" .config 
136:CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=13
207:CONFIG_PRINTK_NMI=y
7758:CONFIG_PRINTK_TIME=y
7759:# CONFIG_PRINTK_CALLER is not set

Do you have any suggestions about the size of CONFIG_LOG_* and CONFIG_PRINTK_* options by default?

Thanks.
Lianbo

> I will move to bare metal x86_64 and hopefully see it as well.
> 
> John
>