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@dplat-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 <[email protected]> Reviewed-by: Kees Cook <[email protected]> Reviewed-by: Petr Mladek <[email protected]> Reviewed-by: Bhupesh Sharma <[email protected]> Acked-by: Baoquan He <[email protected]> --- 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
