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tty: add lockdep annotations

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tty_lock_pair() do the right thing to avoid deadlocks, but should
instruct LOCKDEP of this to avoid a splat.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Dumazet 2012-05-31 11:35:18 +02:00 committed by Linus Torvalds
parent 1d59d61f60
commit fde86d3108
1 changed files with 15 additions and 4 deletions
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19
drivers/tty/tty_mutex.c
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@ -6,11 +6,17 @@
/* Legacy tty mutex glue */ /* Legacy tty mutex glue */
enum {
TTY_MUTEX_NORMAL,
TTY_MUTEX_NESTED,
};
/* /*
* Getting the big tty mutex. * Getting the big tty mutex.
*/ */
void __lockfunc tty_lock(struct tty_struct *tty) static void __lockfunc tty_lock_nested(struct tty_struct *tty,
unsigned int subclass)
{ {
if (tty->magic != TTY_MAGIC) { if (tty->magic != TTY_MAGIC) {
printk(KERN_ERR "L Bad %p\n", tty); printk(KERN_ERR "L Bad %p\n", tty);
@ -18,7 +24,12 @@ void __lockfunc tty_lock(struct tty_struct *tty)
return; return;
} }
tty_kref_get(tty); tty_kref_get(tty);
mutex_lock(&tty->legacy_mutex); mutex_lock_nested(&tty->legacy_mutex, subclass);
}
void __lockfunc tty_lock(struct tty_struct *tty)
{
return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
} }
EXPORT_SYMBOL(tty_lock); EXPORT_SYMBOL(tty_lock);
@ -43,11 +54,11 @@ void __lockfunc tty_lock_pair(struct tty_struct *tty,
{ {
if (tty < tty2) { if (tty < tty2) {
tty_lock(tty); tty_lock(tty);
tty_lock(tty2); tty_lock_nested(tty2, TTY_MUTEX_NESTED);
} else { } else {
if (tty2 && tty2 != tty) if (tty2 && tty2 != tty)
tty_lock(tty2); tty_lock(tty2);
tty_lock(tty); tty_lock_nested(tty, TTY_MUTEX_NESTED);
} }
} }
EXPORT_SYMBOL(tty_lock_pair); EXPORT_SYMBOL(tty_lock_pair);