On 2022-11-16, Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>> /*
>> - * Hold the console_lock to guarantee that no consoles are
>> + * Hold the console_list_lock to guarantee that no consoles are
>> * unregistered until the kgdboc_earlycon setup is complete.
>> * Trapping the exit() callback relies on exit() not being
>> * called until the trap is setup. This also allows safe
>> * traversal of the console list and race-free reading of @flags.
>> */
>> - console_lock();
>> + console_list_lock();
>> for_each_console(con) {
>> if (con->write && con->read &&
>> (con->flags & (CON_BOOT | CON_ENABLED)) &&
>
> Officially don't we need both the list lock and normal lock here since
> we're reaching into the consoles?
AFAICT the only synchronization we need here is iterating the console
list, reading con->flags of a registered console, and modifying
con->exit of a registered console. The console_list_lock provides
synchronization for all of these things. By the end of this series the
console_lock does not provide synchronization for any of these things.
Is there something else that requires synchronization here?
After this series the console_lock is still responsible for:
- serializing console->write() callbacks
- stopping console->write() callbacks
- stopping console->device() callbacks
- synchronizing console->seq
- synchronizing console->dropped
- synchronizing the global @console_suspended
- providing various unclear protection for vt consoles
- some bizarre misuses in bcache
The scope may be larger than the above list. The investigation is still
ongoing.
John
