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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: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr 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: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2025-02-25 10:33:28 -08:00 committed by Boqun Feng
parent 59bed79ffd
commit 6ea9a1781c
3 changed files with 8 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/printk.h
View File

@ -207,6 +207,7 @@ void printk_legacy_allow_panic_sync(void);
extern bool nbcon_device_try_acquire(struct console *con); extern bool nbcon_device_try_acquire(struct console *con);
extern void nbcon_device_release(struct console *con); extern void nbcon_device_release(struct console *con);
void nbcon_atomic_flush_unsafe(void); void nbcon_atomic_flush_unsafe(void);
bool pr_flush(int timeout_ms, bool reset_on_progress);
#else #else
static inline __printf(1, 0) static inline __printf(1, 0)
int vprintk(const char *s, va_list args) 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 #endif
bool this_cpu_in_panic(void); bool this_cpu_in_panic(void);

4
kernel/printk/printk.c
View File

@ -2461,7 +2461,6 @@ asmlinkage __visible int _printk(const char *fmt, ...)
} }
EXPORT_SYMBOL(_printk); 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); static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
#else /* CONFIG_PRINTK */ #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 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; } static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
#endif /* CONFIG_PRINTK */ #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. * Context: Process context. May sleep while acquiring console lock.
* Return: true if all usable printers are caught up. * 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); return __pr_flush(NULL, timeout_ms, reset_on_progress);
} }

1
kernel/reboot.c
View File

@ -704,6 +704,7 @@ void kernel_power_off(void)
migrate_to_reboot_cpu(); migrate_to_reboot_cpu();
syscore_shutdown(); syscore_shutdown();
pr_emerg("Power down\n"); pr_emerg("Power down\n");
pr_flush(1000, true);
kmsg_dump(KMSG_DUMP_SHUTDOWN); kmsg_dump(KMSG_DUMP_SHUTDOWN);
machine_power_off(); machine_power_off();
} }