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tty: tty_io: use console_list_lock for list synchronization 

show_cons_active() uses the console_lock to gather information
on registered consoles. It requires that no consoles are unregistered
until it is finished. The console_list_lock should be used because
list synchronization responsibility will be removed from the
console_lock in a later change.

Note, the console_lock is still needed to serialize the device()
callback with other console operations.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-34-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:45 +01:06 committed by Petr Mladek
parent 6f8836756f
commit 7c2af0f634
1 changed files with 12 additions and 6 deletions
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18
drivers/tty/tty_io.c
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@ -3527,16 +3527,13 @@ static ssize_t show_cons_active(struct device *dev,
ssize_t count = 0;
/*
* Hold the console_lock to guarantee that no consoles are
* Hold the console_list_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();
console_list_lock();
for_each_console(c) {
if (!c->device)
continue;
@ -3548,6 +3545,13 @@ static ssize_t show_cons_active(struct device *dev,
if (i >= ARRAY_SIZE(cs))
break;
}
/*
* 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();
while (i--) {
int index = cs[i]->index;
struct tty_driver *drv = cs[i]->device(cs[i], &index);
@ -3563,6 +3567,8 @@ static ssize_t show_cons_active(struct device *dev,
}
console_unlock();
console_list_unlock();
return count;
}
static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);