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
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;
/**
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;
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.
*/
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
#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
*
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
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);
#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
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
if ((newcon->flags & CON_BOOT) && realcon_registered) {
pr_info("Too late to register bootconsole %s%d\n",
newcon->name, newcon->index);
- return;
+ goto unlock;
}
/*
/* 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,
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);
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);
/*
struct console *con;
int ret;
+ console_list_lock();
hlist_for_each_entry_safe(con, tmp, &console_list, node) {
if (!(con->flags & CON_BOOT))
continue;
*/
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);