From 92fd015cad5857ed7626954cc1bd0fe625f79507 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 28 May 2020 14:35:12 +0200
Subject: [PATCH 502/518] Bluetooth: Acquire sk_lock.slock without disabling
 interrupts

There was a lockdep which led to commit
   fad003b6c8e3d ("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>
(cherry picked from commit e6da0edc24eecef2f6964d92fa9044e1821deace)
Signed-off-by: Clark Williams <williams@redhat.com>
---
 net/bluetooth/rfcomm/sock.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index eeff89e8ad4ce..ee1675370b69d 100644
--- 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
-- 
2.41.0

