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

diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index 46b305f..e0758fe 100644 (file)
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -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 = {