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Message-ID: <20210319193138.GA235401@sequoia>
Date: Fri, 19 Mar 2021 14:31:38 -0500
From: Tyler Hicks <tyhicks@...ux.microsoft.com>
To: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: jmorris@...ei.org, sashal@...nel.org, 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 v3 1/1] kexec: dump kmessage before machine_kexec
On 2021-03-19 15:23:26, 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>
Reviewed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
Tyler
> Acked-by: Baoquan He <bhe@...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 a0b6780740c8..6ee4a1cf6e8e 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>
> @@ -1179,6 +1180,7 @@ int kernel_kexec(void)
> machine_shutdown();
> }
>
> + kmsg_dump(KMSG_DUMP_SHUTDOWN);
> machine_kexec(kexec_image);
>
> #ifdef CONFIG_KEXEC_JUMP
> --
> 2.25.1
>
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