Bluetooth: Acquire sk_lock.slock without disabling interrupts

There was a lockdep which led to commit
   bcacc37bcb8d1 ("Bluetooth: Fix inconsistent lock state with RFCOMM")

Lockdep noticed that `sk->sk_lock.slock' was acquired without disabling
the softirq while the lock was also used in softirq context.
Unfortunately the solution back then was to disable interrupts before
acquiring the lock which however made lockdep happy.
It would have been enough to simply disable the softirq. Disabling
interrupts before acquiring a spinlock_t is not allowed on PREEMPT_RT
because these locks are converted to 'sleeping' spinlocks.

Use spin_lock_bh() in order to acquire the `sk_lock.slock'.

Reported-by: Luis Claudio R. Goncalves <lclaudio@uudg.org>
Reported-by: kbuild test robot <lkp@intel.com> [missing unlock]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index b4eaf21360ef25da6be5fa3c28d1f2764fbced97..df14eebe80da8bc574e2810b235a9bbcddcf042c 100644 (file)
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -64,15 +64,13 @@ static void rfcomm_sk_data_ready(struct rfcomm_dlc *d, struct sk_buff *skb)
 static void rfcomm_sk_state_change(struct rfcomm_dlc *d, int err)
 {
        struct sock *sk = d->owner, *parent;
-       unsigned long flags;
 
        if (!sk)
                return;
 
        BT_DBG("dlc %p state %ld err %d", d, d->state, err);
 
-       local_irq_save(flags);
-       bh_lock_sock(sk);
+       spin_lock_bh(&sk->sk_lock.slock);
 
        if (err)
                sk->sk_err = err;
@@ -93,8 +91,7 @@ static void rfcomm_sk_state_change(struct rfcomm_dlc *d, int err)
                sk->sk_state_change(sk);
        }
 
-       bh_unlock_sock(sk);
-       local_irq_restore(flags);
+       spin_unlock_bh(&sk->sk_lock.slock);
 
        if (parent && sock_flag(sk, SOCK_ZAPPED)) {
                /* We have to drop DLC lock here, otherwise