Commit 6ea9a178 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Boqun Feng
Browse files

Flush console log from kernel_power_off() 



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: default avatarPaul E. McKenney <paulmck@kernel.org>
Reviewed-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Link: https://lore.kernel.org/r/5f743488-dc2a-4f19-bdda-cf50b9314832@paulmck-laptop


Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 59bed79f

include/linux/printk.h

+6 −0
Original line number Diff line number Diff line
@@ -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);

kernel/printk/printk.c

+1 −3
Original line number Diff line number Diff line
@@ -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);

}

kernel/reboot.c

+1 −0
Original line number Diff line number Diff line
@@ -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();

}