Re: [PATCH v1] kernel/reboot: Change registration order of legacy power-off handler
From: Michael Ellerman
Date: Sat Jun 04 2022 - 22:01:44 EST
Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> writes:
> We're unconditionally registering sys-off handler for the legacy
> pm_power_off() callback, this causes problem for platforms that don't
> use power-off handlers at all and should be halted. Now reboot syscall
> assumes that there is a power-off handler installed and tries to power
> off system instead of halting it.
>
> To fix the trouble, move the handler's registration to the reboot syscall
> and check the pm_power_off() presence.
I'm seeing a qemu virtual machine (ppce500) fail to power off using the
gpio-poweroff driver. I bisected it to this commit.
I think the problem is that the machine is going via kernel_power_off(),
not sys_reboot(), and so legacy_pm_power_off() has not been registered.
If I just put the core_initcall back then it works as before. Not sure
if that's a safe change in general though.
cheers
> Fixes: 0e2110d2e910 ("kernel/reboot: Add kernel_can_power_off()")
> Reported-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
> kernel/reboot.c | 33 +++++++++++++++++----------------
> 1 file changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index 0bdc64ecf4f6..a091145ee710 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -569,22 +569,6 @@ static int legacy_pm_power_off(struct sys_off_data *data)
> return NOTIFY_DONE;
> }
>
> -/*
> - * Register sys-off handlers for legacy PM callbacks. This allows legacy
> - * PM callbacks co-exist with the new sys-off API.
> - *
> - * TODO: Remove legacy handlers once all legacy PM users will be switched
> - * to the sys-off based APIs.
> - */
> -static int __init legacy_pm_init(void)
> -{
> - register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT,
> - legacy_pm_power_off, NULL);
> -
> - return 0;
> -}
> -core_initcall(legacy_pm_init);
> -
> static void do_kernel_power_off_prepare(void)
> {
> blocking_notifier_call_chain(&power_off_prep_handler_list, 0, NULL);
> @@ -646,6 +630,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
> void __user *, arg)
> {
> struct pid_namespace *pid_ns = task_active_pid_ns(current);
> + struct sys_off_handler *sys_off = NULL;
> char buffer[256];
> int ret = 0;
>
> @@ -670,6 +655,21 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
> if (ret)
> return ret;
>
> + /*
> + * Register sys-off handlers for legacy PM callback. This allows
> + * legacy PM callbacks temporary co-exist with the new sys-off API.
> + *
> + * TODO: Remove legacy handlers once all legacy PM users will be
> + * switched to the sys-off based APIs.
> + */
> + if (pm_power_off) {
> + sys_off = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
> + SYS_OFF_PRIO_DEFAULT,
> + legacy_pm_power_off, NULL);
> + if (IS_ERR(sys_off))
> + return PTR_ERR(sys_off);
> + }
> +
> /* Instead of trying to make the power_off code look like
> * halt when pm_power_off is not set do it the easy way.
> */
> @@ -727,6 +727,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
> break;
> }
> mutex_unlock(&system_transition_mutex);
> + unregister_sys_off_handler(sys_off);
> return ret;
> }
>
> --
> 2.35.3