diff options
| -rw-r--r-- | include/linux/printk.h | 4 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 77 |
2 files changed, 57 insertions, 24 deletions
diff --git a/include/linux/printk.h b/include/linux/printk.h index 5e038e782256..1c5936ab991f 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -195,6 +195,7 @@ void show_regs_print_info(const char *log_lvl); extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; extern asmlinkage void dump_stack(void) __cold; void printk_trigger_flush(void); +void console_replay_all(void); #else static inline __printf(1, 0) int vprintk(const char *s, va_list args) @@ -274,6 +275,9 @@ static inline void dump_stack(void) static inline void printk_trigger_flush(void) { } +static inline void console_replay_all(void) +{ +} #endif bool this_cpu_in_panic(void); diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1e3b21682547..6206804d275b 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3161,6 +3161,40 @@ void console_unblank(void) pr_flush(1000, true); } +/* + * Rewind all consoles to the oldest available record. + * + * IMPORTANT: The function is safe only when called under + * console_lock(). It is not enforced because + * it is used as a best effort in panic(). + */ +static void __console_rewind_all(void) +{ + struct console *c; + short flags; + int cookie; + u64 seq; + + seq = prb_first_valid_seq(prb); + + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + flags = console_srcu_read_flags(c); + + if (flags & CON_NBCON) { + nbcon_seq_force(c, seq); + } else { + /* + * This assignment is safe only when called under + * console_lock(). On panic, legacy consoles are + * only best effort. + */ + c->seq = seq; + } + } + console_srcu_read_unlock(cookie); +} + /** * console_flush_on_panic - flush console content on panic * @mode: flush all messages in buffer or just the pending ones @@ -3189,30 +3223,8 @@ void console_flush_on_panic(enum con_flush_mode mode) */ console_may_schedule = 0; - if (mode == CONSOLE_REPLAY_ALL) { - struct console *c; - short flags; - int cookie; - u64 seq; - - seq = prb_first_valid_seq(prb); - - cookie = console_srcu_read_lock(); - for_each_console_srcu(c) { - flags = console_srcu_read_flags(c); - - if (flags & CON_NBCON) { - nbcon_seq_force(c, seq); - } else { - /* - * This is an unsynchronized assignment. On - * panic legacy consoles are only best effort. - */ - c->seq = seq; - } - } - console_srcu_read_unlock(cookie); - } + if (mode == CONSOLE_REPLAY_ALL) + __console_rewind_all(); console_flush_all(false, &next_seq, &handover); } @@ -4301,6 +4313,23 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter) } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); +/** + * console_replay_all - replay kernel log on consoles + * + * Try to obtain lock on console subsystem and replay all + * available records in printk buffer on the consoles. + * Does nothing if lock is not obtained. + * + * Context: Any context. + */ +void console_replay_all(void) +{ + if (console_trylock()) { + __console_rewind_all(); + /* Consoles are flushed as part of console_unlock(). */ + console_unlock(); + } +} #endif #ifdef CONFIG_SMP |