linux-kernel - [PATCH rcu 07/10] Flush console log from kernel_power

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Message-ID: <20250305030505.94059-8-boqun.feng@gmail.com>
Date: Tue,  4 Mar 2025 19:05:02 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Petr Mladek <pmladek@...e.com>,	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <clrkwllms@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,	Yuntao Wang <ytcoode@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Guo Weikang <guoweikang.kernel@...il.com>,	KP Singh <kpsingh@...nel.org>,
	Huang Shijie <shijie@...amperecomputing.com>,
	Raul E Rangel <rrangel@...omium.org>,
	Joel Granados <joel.granados@...nel.org>,
	Anna Schumaker <anna.schumaker@...cle.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	zhangguopeng <zhangguopeng@...inos.cn>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Neeraj Upadhyay (AMD)" <neeraj.iitr10@...il.com>,
	linux-kernel@...r.kernel.org,	linux-kselftest@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev
Subject: [PATCH rcu 07/10] Flush console log from kernel_power_off()

From: "Paul E. McKenney" <paulmck@...nel.org>

Kernels built with CONFIG_PREEMPT_RT=y can lose significant console output
and shutdown time, which hides shutdown-time RCU issues from rcutorture.
Therefore, make pr_flush() public and invoke it after then last print
in kernel_power_off().

[ paulmck: Apply John Ogness feedback. ]
[ paulmck: Appy Sebastian Andrzej Siewior feedback. ]
[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: John Ogness <john.ogness@...utronix.de>
Reviewed-by: Petr Mladek <pmladek@...e.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>
Link: https://lore.kernel.org/r/5f743488-dc2a-4f19-bdda-cf50b9314832@paulmck-laptop
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 include/linux/printk.h | 6 ++++++
 kernel/printk/printk.c | 4 +---
 kernel/reboot.c        | 1 +
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 4217a9f412b2..5b462029d03c 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -207,6 +207,7 @@ void printk_legacy_allow_panic_sync(void);
 extern bool nbcon_device_try_acquire(struct console *con);
 extern void nbcon_device_release(struct console *con);
 void nbcon_atomic_flush_unsafe(void);
+bool pr_flush(int timeout_ms, bool reset_on_progress);
 #else
 static inline __printf(1, 0)
 int vprintk(const char *s, va_list args)
@@ -315,6 +316,11 @@ static inline void nbcon_atomic_flush_unsafe(void)
 {
 }
 
+static inline bool pr_flush(int timeout_ms, bool reset_on_progress)
+{
+	return true;
+}
+
 #endif
 
 bool this_cpu_in_panic(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 07668433644b..057db78876cd 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2461,7 +2461,6 @@ asmlinkage __visible int _printk(const char *fmt, ...)
 }
 EXPORT_SYMBOL(_printk);
 
-static bool pr_flush(int timeout_ms, bool reset_on_progress);
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
 
 #else /* CONFIG_PRINTK */
@@ -2474,7 +2473,6 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
 
 static u64 syslog_seq;
 
-static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
 
 #endif /* CONFIG_PRINTK */
@@ -4466,7 +4464,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
  * Context: Process context. May sleep while acquiring console lock.
  * Return: true if all usable printers are caught up.
  */
-static bool pr_flush(int timeout_ms, bool reset_on_progress)
+bool pr_flush(int timeout_ms, bool reset_on_progress)
 {
 	return __pr_flush(NULL, timeout_ms, reset_on_progress);
 }
diff --git a/kernel/reboot.c b/kernel/reboot.c
index b5a8569e5d81..41ab9e1ba357 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -704,6 +704,7 @@ void kernel_power_off(void)
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("Power down\n");
+	pr_flush(1000, true);
 	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_power_off();
 }
-- 
2.48.1