diff options
Diffstat (limited to 'kernel/printk/printk.c')
| -rw-r--r-- | kernel/printk/printk.c | 49 |
1 files changed, 46 insertions, 3 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e58a6ccb945c..bda9e8ec6817 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -248,9 +248,10 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, 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. + * In unregister_console() and console_force_preferred_locked(), + * 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 @@ -3490,6 +3491,48 @@ int unregister_console(struct console *console) } EXPORT_SYMBOL(unregister_console); +/** + * console_force_preferred_locked - force a registered console preferred + * @con: The registered console to force preferred. + * + * Must be called under console_list_lock(). + */ +void console_force_preferred_locked(struct console *con) +{ + struct console *cur_pref_con; + + if (!console_is_registered_locked(con)) + return; + + cur_pref_con = console_first(); + + /* Already preferred? */ + if (cur_pref_con == con) + return; + + /* + * Delete, but do not re-initialize the entry. This allows the console + * to continue to appear registered (via any hlist_unhashed_lockless() + * checks), even though it was briefly removed from the console list. + */ + hlist_del_rcu(&con->node); + + /* + * Ensure that all SRCU list walks have completed so that the console + * can be added to the beginning of the console list and its forward + * list pointer can be re-initialized. + */ + synchronize_srcu(&console_srcu); + + con->flags |= CON_CONSDEV; + WARN_ON(!con->device); + + /* Only the new head can have CON_CONSDEV set. */ + console_srcu_write_flags(cur_pref_con, cur_pref_con->flags & ~CON_CONSDEV); + hlist_add_head_rcu(&con->node, &console_list); +} +EXPORT_SYMBOL(console_force_preferred_locked); + /* * Initialize the console device. This is called *early*, so * we can't necessarily depend on lots of kernel help here. |