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proc: consoles: use console_list_lock for list iteration 

The console_lock is used in part to guarantee safe list iteration.
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: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-35-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:46 +01:06 committed by Petr Mladek
parent 7c2af0f634
commit 28de287a95
1 changed files with 12 additions and 7 deletions
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19
fs/proc/consoles.c
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@ -33,7 +33,16 @@ static int show_console_dev(struct seq_file *m, void *v)
if (con->device) {
const struct tty_driver *driver;
int index;
/*
* 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();
driver = con->device(con, &index);
console_unlock();
if (driver) {
dev = MKDEV(driver->major, driver->minor_start);
dev += index;
@ -64,15 +73,11 @@ static void *c_start(struct seq_file *m, loff_t *pos)
loff_t off = 0;
/*
* Take console_lock to serialize device() callback with
* other console operations. For example, fg_console is
* modified under console_lock when switching vt.
*
* Hold the console_lock to guarantee safe traversal of the
* Hold the console_list_lock to guarantee safe traversal of the
* console list. SRCU cannot be used because there is no
* place to store the SRCU cookie.
*/
console_lock();
console_list_lock();
for_each_console(con)
if (off++ == *pos)
break;
@ -90,7 +95,7 @@ static void *c_next(struct seq_file *m, void *v, loff_t *pos)
static void c_stop(struct seq_file *m, void *v)
{
console_unlock();
console_list_unlock();
}
static const struct seq_operations consoles_op = {