2023-03-20 21:34:04

by Benjamin Bara

Subject: [PATCH] kernel/reboot: emergency_restart: set correct system_state

From: Benjamin Bara <[email protected]>

As the emergency restart does not call kernel_restart_prepare(),
the system_state stays in SYSTEM_RUNNING.

This e.g. hinders i2c_in_atomic_xfer_mode() from becoming active,
and therefore might lead to avoidable warnings in the restart handlers,
e.g.:
[ 12.667612] WARNING: CPU: 1 PID: 1 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch+0x33c/0x6b0
[ 12.676926] Voluntary context switch within RCU read-side critical section!
...
[ 12.742376] schedule_timeout from wait_for_completion_timeout+0x90/0x114
[ 12.749179] wait_for_completion_timeout from tegra_i2c_wait_completion+0x40/0x70
...
[ 12.994527] atomic_notifier_call_chain from machine_restart+0x34/0x58
[ 13.001050] machine_restart from panic+0x2a8/0x32c

Avoid these by setting the correct system_state.

Signed-off-by: Benjamin Bara <[email protected]>
---
kernel/reboot.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/reboot.c b/kernel/reboot.c
index 3bba88c7ffc6..6ebef11c8876 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -74,6 +74,7 @@ void __weak (*pm_power_off)(void);
void emergency_restart(void)
{
kmsg_dump(KMSG_DUMP_EMERG);
+ system_state = SYSTEM_RESTART;
machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);
--
2.34.1

2023-03-21 02:12:29

by Dmitry Osipenko

Subject: Re: [PATCH] kernel/reboot: emergency_restart: set correct system_state

On 3/21/23 00:32, Benjamin Bara wrote:
> From: Benjamin Bara <[email protected]>
>
> As the emergency restart does not call kernel_restart_prepare(),
> the system_state stays in SYSTEM_RUNNING.
>
> This e.g. hinders i2c_in_atomic_xfer_mode() from becoming active,
> and therefore might lead to avoidable warnings in the restart handlers,
> e.g.:
> [ 12.667612] WARNING: CPU: 1 PID: 1 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch+0x33c/0x6b0
> [ 12.676926] Voluntary context switch within RCU read-side critical section!
> ...
> [ 12.742376] schedule_timeout from wait_for_completion_timeout+0x90/0x114
> [ 12.749179] wait_for_completion_timeout from tegra_i2c_wait_completion+0x40/0x70
> ...
> [ 12.994527] atomic_notifier_call_chain from machine_restart+0x34/0x58
> [ 13.001050] machine_restart from panic+0x2a8/0x32c
>
> Avoid these by setting the correct system_state.
>
> Signed-off-by: Benjamin Bara <[email protected]>
> ---
> kernel/reboot.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index 3bba88c7ffc6..6ebef11c8876 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -74,6 +74,7 @@ void __weak (*pm_power_off)(void);
> void emergency_restart(void)
> {
> kmsg_dump(KMSG_DUMP_EMERG);
> + system_state = SYSTEM_RESTART;
> machine_emergency_restart();
> }
> EXPORT_SYMBOL_GPL(emergency_restart);

This patch needs to be paired with the i2c_in_atomic_xfer_mode() change.
Please also add the v5.2+ stable tag to the commit messages.

--
Best regards,
Dmitry