diff options
| -rw-r--r-- | kernel/printk/printk.c | 39 |
1 files changed, 34 insertions, 5 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c6e633329e4d..b3ddcf39a53c 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -464,6 +464,13 @@ static int console_msg_format = MSG_FORMAT_DEFAULT; static DEFINE_MUTEX(syslog_lock); /* + * Specifies if a legacy console is registered. If legacy consoles are + * present, it is necessary to perform the console lock/unlock dance + * whenever console flushing should occur. + */ +static bool have_legacy_console; + +/* * Specifies if a boot console is registered. If boot consoles are present, * nbcon consoles cannot print simultaneously and must be synchronized by * the console lock. This is because boot consoles and nbcon consoles may @@ -471,6 +478,14 @@ static DEFINE_MUTEX(syslog_lock); */ bool have_boot_console; +/* + * Specifies if the console lock/unlock dance is needed for console + * printing. If @have_boot_console is true, the nbcon consoles will + * be printed serially along with the legacy consoles because nbcon + * consoles cannot print simultaneously with boot consoles. + */ +#define printing_via_unlock (have_legacy_console || have_boot_console) + #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); /* All 3 protected by @syslog_lock. */ @@ -2339,7 +2354,7 @@ asmlinkage int vprintk_emit(int facility, int level, printed_len = vprintk_store(facility, level, dev_info, fmt, args); /* If called from the scheduler, we can not call up(). */ - if (!in_sched) { + if (!in_sched && printing_via_unlock) { /* * The caller may be holding system-critical or * timing-sensitive locks. Disable preemption during @@ -2359,7 +2374,7 @@ asmlinkage int vprintk_emit(int facility, int level, preempt_enable(); } - if (in_sched) + if (in_sched && printing_via_unlock) defer_console_output(); else wake_up_klogd(); @@ -2718,7 +2733,7 @@ void resume_console(void) */ static int console_cpu_notify(unsigned int cpu) { - if (!cpuhp_tasks_frozen) { + if (!cpuhp_tasks_frozen && printing_via_unlock) { /* If trylock fails, someone else is doing the printing */ if (console_trylock()) console_unlock(); @@ -3625,6 +3640,7 @@ void register_console(struct console *newcon) if (newcon->flags & CON_NBCON) { nbcon_seq_force(newcon, init_seq); } else { + have_legacy_console = true; newcon->seq = init_seq; } @@ -3701,6 +3717,7 @@ EXPORT_SYMBOL(register_console); static int unregister_console_locked(struct console *console) { bool use_device_lock = (console->flags & CON_NBCON) && console->write_atomic; + bool found_legacy_con = false; bool found_boot_con = false; unsigned long flags; struct console *c; @@ -3768,9 +3785,13 @@ static int unregister_console_locked(struct console *console) for_each_console(c) { if (c->flags & CON_BOOT) found_boot_con = true; + if (!(c->flags & CON_NBCON)) + found_legacy_con = true; } if (!found_boot_con) have_boot_console = found_boot_con; + if (!found_legacy_con) + have_legacy_console = found_legacy_con; return res; } @@ -3931,8 +3952,10 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre seq = prb_next_reserve_seq(prb); /* Flush the consoles so that records up to @seq are printed. */ - console_lock(); - console_unlock(); + if (printing_via_unlock) { + console_lock(); + console_unlock(); + } for (;;) { unsigned long begin_jiffies; @@ -3945,6 +3968,12 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre * console->seq. Releasing console_lock flushes more * records in case @seq is still not printed on all * usable consoles. + * + * Holding the console_lock is not necessary if there + * are no legacy or boot consoles. However, such a + * console could register at any time. Always hold the + * console_lock as a precaution rather than + * synchronizing against register_console(). */ console_lock(); |