diff options
| -rw-r--r-- | include/linux/printk.h | 5 | ||||
| -rw-r--r-- | kernel/panic.c | 2 | ||||
| -rw-r--r-- | kernel/printk/internal.h | 1 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 55 |
4 files changed, 56 insertions, 7 deletions
diff --git a/include/linux/printk.h b/include/linux/printk.h index 2e083f01f8a3..eca9bb2ee637 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -200,6 +200,7 @@ 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_try_replay_all(void); +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); @@ -286,6 +287,10 @@ static inline void console_try_replay_all(void) { } +static inline void printk_legacy_allow_panic_sync(void) +{ +} + static inline bool nbcon_device_try_acquire(struct console *con) { return false; diff --git a/kernel/panic.c b/kernel/panic.c index df37c913b010..93096d5abcc7 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -374,6 +374,8 @@ void panic(const char *fmt, ...) panic_other_cpus_shutdown(_crash_kexec_post_notifiers); + printk_legacy_allow_panic_sync(); + /* * Run any panic handlers, including those that might need to * add information to the kmsg dump output. diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 7679e18f24b3..6b61350a3026 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -154,6 +154,7 @@ static inline bool console_is_usable(struct console *con, short flags) { return #endif /* CONFIG_PRINTK */ extern bool have_boot_console; +extern bool legacy_allow_panic_sync; extern struct printk_buffers printk_shared_pbufs; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e30107d216a5..fc3f8970eea2 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -471,7 +471,9 @@ static DEFINE_MUTEX(syslog_lock); static bool have_legacy_console; /* - * Specifies if an nbcon console is registered. + * Specifies if an nbcon console is registered. If nbcon consoles are present, + * synchronous printing of legacy consoles will not occur during panic until + * the backtrace has been stored to the ringbuffer. */ static bool have_nbcon_console; @@ -483,6 +485,9 @@ static bool have_nbcon_console; */ bool have_boot_console; +/* See printk_legacy_allow_panic_sync() for details. */ +bool legacy_allow_panic_sync; + /* * Specifies if the console lock/unlock dance is needed for console * printing. If @have_boot_console is true, the nbcon consoles will @@ -2330,12 +2335,28 @@ out: return ret; } +/* + * This acts as a one-way switch to allow legacy consoles to print from + * the printk() caller context on a panic CPU. It also attempts to flush + * the legacy consoles in this context. + */ +void printk_legacy_allow_panic_sync(void) +{ + legacy_allow_panic_sync = true; + + if (printing_via_unlock && !is_printk_legacy_deferred()) { + if (console_trylock()) + console_unlock(); + } +} + asmlinkage int vprintk_emit(int facility, int level, const struct dev_printk_info *dev_info, const char *fmt, va_list args) { + bool do_trylock_unlock = printing_via_unlock; + bool defer_legacy = false; int printed_len; - bool in_sched = false; /* Suppress unimportant messages after panic happens */ if (unlikely(suppress_printk)) @@ -2349,17 +2370,35 @@ asmlinkage int vprintk_emit(int facility, int level, if (other_cpu_in_panic() && !panic_triggering_all_cpu_backtrace) return 0; + /* If called from the scheduler, we can not call up(). */ if (level == LOGLEVEL_SCHED) { level = LOGLEVEL_DEFAULT; - in_sched = true; + defer_legacy = do_trylock_unlock; + do_trylock_unlock = false; } printk_delay(level); printed_len = vprintk_store(facility, level, dev_info, fmt, args); - /* If called from the scheduler, we can not call up(). */ - if (!in_sched && printing_via_unlock) { + if (have_nbcon_console && !have_boot_console) { + nbcon_atomic_flush_pending(); + + /* + * In panic, the legacy consoles are not allowed to print from + * the printk calling context unless explicitly allowed. This + * gives the safe nbcon consoles a chance to print out all the + * panic messages first. This restriction only applies if + * there are nbcon consoles registered and they are allowed to + * flush. + */ + if (this_cpu_in_panic() && !legacy_allow_panic_sync) { + do_trylock_unlock = false; + defer_legacy = false; + } + } + + if (do_trylock_unlock) { /* * The caller may be holding system-critical or * timing-sensitive locks. Disable preemption during @@ -2379,7 +2418,7 @@ asmlinkage int vprintk_emit(int facility, int level, preempt_enable(); } - if (in_sched && printing_via_unlock) + if (defer_legacy) defer_console_output(); else wake_up_klogd(); @@ -3292,7 +3331,9 @@ void console_flush_on_panic(enum con_flush_mode mode) if (!have_boot_console) nbcon_atomic_flush_pending(); - console_flush_all(false, &next_seq, &handover); + /* Flush legacy consoles once allowed, even when dangerous. */ + if (legacy_allow_panic_sync) + console_flush_all(false, &next_seq, &handover); } /* |