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Diffstat (limited to 'kernel/printk/printk.c')
-rw-r--r--kernel/printk/printk.c89
1 files changed, 80 insertions, 9 deletions
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);