Re: [PATCH printk v2 02/38] printk: Convert console_drivers list to hlist

John Ogness
2022-10-19T21:47:02Z

On 2022-10-19, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index e4f1e7478b52..867becc40021 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
>> if (res > 0)
>> return 0;
>>
>> - res = -ENODEV;
>> console_lock();
>> - if (console_drivers == console) {
>> - console_drivers=console->next;
>> - res = 0;
>> - } else {
>> - for_each_console(con) {
>> - if (con->next == console) {
>> - con->next = console->next;
>> - res = 0;
>> - break;
>> - }
>> - }
>> +
>> + /* Disable it unconditionally */
>> + console->flags &= ~CON_ENABLED;
>> +
>> + if (hlist_unhashed(&console->node)) {
>
> How can this ever be hit? The console lock is held, so it shouldn't
> have gone away already. Or am I missing something else here?

Mainline also has this check. I expect it is for the case that some code
tries to call unregister_console() for a console that is not
registered.

Since register_console() does not return if it succeeded, I suppose some
code somewhere my try to unregister without knowing that it never
registered in the first place.

> Other than that minor question, looks good to me!
>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Thanks!

John