diff options
| -rw-r--r-- | include/linux/console.h | 23 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 89 |
2 files changed, 100 insertions, 12 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index f4f0c9523835..24d83e24840b 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -158,6 +158,14 @@ struct console { struct hlist_node node; }; +#ifdef CONFIG_LOCKDEP +extern void lockdep_assert_console_list_lock_held(void); +#else +static inline void lockdep_assert_console_list_lock_held(void) +{ +} +#endif + #ifdef CONFIG_DEBUG_LOCK_ALLOC extern bool console_srcu_read_lock_is_held(void); #else @@ -170,6 +178,9 @@ static inline bool console_srcu_read_lock_is_held(void) extern int console_srcu_read_lock(void); extern void console_srcu_read_unlock(int cookie); +extern void console_list_lock(void) __acquires(console_mutex); +extern void console_list_unlock(void) __releases(console_mutex); + extern struct hlist_head console_list; /** @@ -186,10 +197,16 @@ extern struct hlist_head console_list; hlist_for_each_entry_srcu(con, &console_list, node, \ console_srcu_read_lock_is_held()) -/* - * for_each_console() allows you to iterate on each console +/** + * for_each_console() - Iterator over registered consoles + * @con: struct console pointer used as loop cursor + * + * The console list and the console->flags are immutable while iterating. + * + * Requires console_list_lock to be held. */ -#define for_each_console(con) \ +#define for_each_console(con) \ + lockdep_assert_console_list_lock_held(); \ hlist_for_each_entry(con, &console_list, node) extern int console_set_on_cmdline; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c84654444a02..2b4506673a86 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -79,6 +79,13 @@ int oops_in_progress; EXPORT_SYMBOL(oops_in_progress); /* + * console_mutex protects console_list updates and console->flags updates. + * The flags are synchronized only for consoles that are registered, i.e. + * accessible via the console list. + */ +static DEFINE_MUTEX(console_mutex); + +/* * console_sem protects console_list and console->flags updates, and also * provides serialization for access to the entire console driver system. */ @@ -103,6 +110,12 @@ static int __read_mostly suppress_panic_printk; static struct lockdep_map console_lock_dep_map = { .name = "console_lock" }; + +void lockdep_assert_console_list_lock_held(void) +{ + lockdep_assert_held(&console_mutex); +} +EXPORT_SYMBOL(lockdep_assert_console_list_lock_held); #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -228,6 +241,40 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, #endif /* CONFIG_PRINTK && CONFIG_SYSCTL */ /** + * console_list_lock - Lock the console list + * + * For console list or console->flags updates + */ +void console_list_lock(void) +{ + /* + * In unregister_console(), synchronize_srcu() is called with the + * console_list_lock held. Therefore it is not allowed that the + * console_list_lock is taken with the srcu_lock held. + * + * Detecting if this context is really in the read-side critical + * section is only possible if the appropriate debug options are + * enabled. + */ + WARN_ON_ONCE(debug_lockdep_rcu_enabled() && + srcu_read_lock_held(&console_srcu)); + + mutex_lock(&console_mutex); +} +EXPORT_SYMBOL(console_list_lock); + +/** + * console_list_unlock - Unlock the console list + * + * Counterpart to console_list_lock() + */ +void console_list_unlock(void) +{ + mutex_unlock(&console_mutex); +} +EXPORT_SYMBOL(console_list_unlock); + +/** * console_srcu_read_lock - Register a new reader for the * SRCU-protected console list * @@ -3020,9 +3067,11 @@ struct tty_driver *console_device(int *index) void console_stop(struct console *console) { __pr_flush(console, 1000, true); + console_list_lock(); console_lock(); console->flags &= ~CON_ENABLED; console_unlock(); + console_list_unlock(); /* * Ensure that all SRCU list walks have completed. All contexts must @@ -3036,9 +3085,11 @@ EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { + console_list_lock(); console_lock(); console->flags |= CON_ENABLED; console_unlock(); + console_list_unlock(); __pr_flush(console, 1000, true); } EXPORT_SYMBOL(console_start); @@ -3187,6 +3238,8 @@ static void console_init_seq(struct console *newcon, bool bootcon_registered) #define console_first() \ hlist_entry(console_list.first, struct console, node) +static int unregister_console_locked(struct console *console); + /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to @@ -3213,13 +3266,14 @@ void register_console(struct console *newcon) bool realcon_registered = false; int err; + console_list_lock(); + for_each_console(con) { if (WARN(con == newcon, "console '%s%d' already registered\n", - con->name, con->index)) - return; - } + con->name, con->index)) { + goto unlock; + } - for_each_console(con) { if (con->flags & CON_BOOT) bootcon_registered = true; else @@ -3230,7 +3284,7 @@ void register_console(struct console *newcon) if ((newcon->flags & CON_BOOT) && realcon_registered) { pr_info("Too late to register bootconsole %s%d\n", newcon->name, newcon->index); - return; + goto unlock; } /* @@ -3261,7 +3315,7 @@ void register_console(struct console *newcon) /* printk() messages are not printed to the Braille console. */ if (err || newcon->flags & CON_BRL) - return; + goto unlock; /* * If we have a bootconsole, and are switching to a real console, @@ -3320,16 +3374,21 @@ void register_console(struct console *newcon) hlist_for_each_entry_safe(con, tmp, &console_list, node) { if (con->flags & CON_BOOT) - unregister_console(con); + unregister_console_locked(con); } } +unlock: + console_list_unlock(); } EXPORT_SYMBOL(register_console); -int unregister_console(struct console *console) +/* Must be called under console_list_lock(). */ +static int unregister_console_locked(struct console *console) { int res; + lockdep_assert_console_list_lock_held(); + con_printk(KERN_INFO, console, "disabled\n"); res = _braille_unregister_console(console); @@ -3378,6 +3437,16 @@ int unregister_console(struct console *console) return res; } + +int unregister_console(struct console *console) +{ + int res; + + console_list_lock(); + res = unregister_console_locked(console); + console_list_unlock(); + return res; +} EXPORT_SYMBOL(unregister_console); /* @@ -3430,6 +3499,7 @@ static int __init printk_late_init(void) struct console *con; int ret; + console_list_lock(); hlist_for_each_entry_safe(con, tmp, &console_list, node) { if (!(con->flags & CON_BOOT)) continue; @@ -3447,9 +3517,10 @@ static int __init printk_late_init(void) */ pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", con->name, con->index); - unregister_console(con); + unregister_console_locked(con); } } + console_list_unlock(); ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, console_cpu_notify); |