linux-kernel - [PATCH v3 1/4] kernel/reboot: emergency_restart: set correct system

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Date:   Mon, 27 Mar 2023 15:57:43 +0200
From:   Benjamin Bara <bbara93@...il.com>
To:     Wolfram Sang <wsa@...nel.org>, Lee Jones <lee@...nel.org>,
        rafael.j.wysocki@...el.com
Cc:     dmitry.osipenko@...labora.com, jonathanh@...dia.com,
        richard.leitner@...ux.dev, treding@...dia.com,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        Benjamin Bara <benjamin.bara@...data.com>,
        stable@...r.kernel.org
Subject: [PATCH v3 1/4] kernel/reboot: emergency_restart: set correct
 system_state

From: Benjamin Bara <benjamin.bara@...data.com>

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.

Cc: stable@...r.kernel.org # v5.2+
Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
---
 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