linux-kernel - Re: [PATCH] kexec: quiet down kexec reboot

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Date:   Thu, 25 Apr 2019 17:32:00 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, sashal@...nel.org, ebiederm@...ssion.com,
        dyoung@...hat.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kexec: quiet down kexec reboot

On 04/23/19 at 04:41pm, Pavel Tatashin wrote:
> Here is a regular kexec command sequence and output:
> =====
> $ kexec --reuse-cmdline -i --load Image
> $ kexec -e
> [  161.342002] kexec_core: Starting new kernel
> 
> Welcome to Buildroot
> buildroot login:
> =====
> 
> Even when "quiet" kernel parameter is specified, "kexec_core: Starting
> new kernel" is printed.

I personally don't like this change very much. 

kernel-parameters.txt tells that quiet disables most log messages, but
not to disable log messages.

	quiet           [KNL] Disable most log messages 

And kexec doesn't print many messages. When 'kexec -e' is executed,
much critical work need be done in 1st kernel, and also in 2nd kernel
till printed messages are seen. Sometime it could hang there without a
notice, because we need shutdown all devices before it. Keeping it can
at least tell which stage it is?

No strong objection, just we may need enable it manually if silent
hang is met. Anyone has different opinion? 

Thanks
Baoquan

> 
> This message has  KERN_EMERG level, but there is no emergency, it is
> a normal kexec operation, so quiet it down to appropriate KERN_NOTICE.
> 
> Machines that have slow console baud rate benefit from less output.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> ---
>  kernel/kexec_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index d7140447be75..fe13e86984ec 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1171,7 +1171,7 @@ int kernel_kexec(void)
>  		 * CPU hotplug again; so re-enable it here.
>  		 */
>  		cpu_hotplug_enable();
> -		pr_emerg("Starting new kernel\n");
> +		pr_notice("Starting new kernel\n");
>  		machine_shutdown();
>  	}
>  
> -- 
> 2.21.0
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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