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tty: tty_io: document console_lock usage 

show_cons_active() uses the console_lock to gather information
on registered consoles. Since the console_lock is being used for
multiple reasons, explicitly document these reasons. This will
be useful when the console_lock is split into fine-grained
locking.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-10-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:21 +01:06 committed by Petr Mladek
parent 0fb413ea64
commit d25a2e748a
1 changed files with 10 additions and 0 deletions
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10
drivers/tty/tty_io.c
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@ -3526,6 +3526,16 @@ static ssize_t show_cons_active(struct device *dev,
struct console *c;
ssize_t count = 0;
/*
* Hold the console_lock to guarantee that no consoles are
* unregistered until all console processing is complete.
* This also allows safe traversal of the console list and
* race-free reading of @flags.
*
* Take console_lock to serialize device() callback with
* other console operations. For example, fg_console is
* modified under console_lock when switching vt.
*/
console_lock();
for_each_console(c) {
if (!c->device)