linux-kernel - Re: [PATCH v2 1/1] kexec: dump kmessage before machine_kexec

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Date:   Thu, 28 Jan 2021 13:22:08 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, sashal@...nel.org, tyhicks@...ux.microsoft.com,
        pmladek@...e.com, ebiederm@...ssion.com, keescook@...omium.org,
        anton@...msg.org, ccross@...roid.com, tony.luck@...el.com,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org
Subject: Re: [PATCH v2 1/1] kexec: dump kmessage before machine_kexec

On 01/26/21 at 03:41pm, Pavel Tatashin wrote:
> kmsg_dump(KMSG_DUMP_SHUTDOWN) is called before
> machine_restart(), machine_halt(), machine_power_off(), the only one that
> is missing is  machine_kexec().
> 
> The dmesg output that it contains can be used to study the shutdown
> performance of both kernel and systemd during kexec reboot.
> 
> Here is example of dmesg data collected after kexec:
> 
> root@...at-cp22:~# cat /sys/fs/pstore/dmesg-ramoops-0 | tail
> ...
> <6>[   70.914592] psci: CPU3 killed (polled 0 ms)
> <5>[   70.915705] CPU4: shutdown
> <6>[   70.916643] psci: CPU4 killed (polled 4 ms)
> <5>[   70.917715] CPU5: shutdown
> <6>[   70.918725] psci: CPU5 killed (polled 0 ms)
> <5>[   70.919704] CPU6: shutdown
> <6>[   70.920726] psci: CPU6 killed (polled 4 ms)
> <5>[   70.921642] CPU7: shutdown
> <6>[   70.922650] psci: CPU7 killed (polled 0 ms)
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> Reviewed-by: Bhupesh Sharma <bhsharma@...hat.com>
> ---
>  kernel/kexec_core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 4f8efc278aa7..e253c8b59145 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -37,6 +37,7 @@
>  #include <linux/compiler.h>
>  #include <linux/hugetlb.h>
>  #include <linux/objtool.h>
> +#include <linux/kmsg_dump.h>
>  
>  #include <asm/page.h>
>  #include <asm/sections.h>
> @@ -1180,6 +1181,7 @@ int kernel_kexec(void)
>  		machine_shutdown();
>  	}
>  
> +	kmsg_dump(KMSG_DUMP_SHUTDOWN);
>  	machine_kexec(kexec_image);

Looks good to me, thx.

Acked-by: Baoquan He <bhe@...hat.com>

>  
>  #ifdef CONFIG_KEXEC_JUMP
> -- 
> 2.25.1
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 

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