From: Peter Zijlstra ============================================= [ INFO: possible recursive locking detected ] 2.6.18-1.2726.fc6 #1 --------------------------------------------- hidd/2271 is trying to acquire lock: (sk_lock-AF_BLUETOOTH){--..}, at: [] bt_accept_dequeue+0x26/0xc6 [bluetooth] but task is already holding lock: (sk_lock-AF_BLUETOOTH){--..}, at: [] l2cap_sock_accept+0x41/0x11e [l2cap] other info that might help us debug this: 1 lock held by hidd/2271: #0: (sk_lock-AF_BLUETOOTH){--..}, at: [] l2cap_sock_accept+0x41/0x11e [l2cap] stack backtrace: [] show_trace_log_lvl+0x58/0x16a [] show_trace+0xd/0x10 [] dump_stack+0x19/0x1b [] __lock_acquire+0x6ea/0x90d [] lock_acquire+0x4b/0x6b [] lock_sock+0xac/0xbc [] bt_accept_dequeue+0x26/0xc6 [bluetooth] [] l2cap_sock_accept+0xe2/0x11e [l2cap] [] sys_accept+0xd8/0x179 [] sys_socketcall+0xa7/0x186 [] syscall_call+0x7/0xb classical case of nesting; bt_accept_dequeue() locks the children of the object locked by l2cap_sock_accept(). Signed-off-by: Peter Zijlstra Acked-by: Marcel Holtmann Signed-off-by: Andrew Morton --- include/net/sock.h | 8 +++++++- net/bluetooth/l2cap.c | 4 ++-- net/core/sock.c | 6 +++--- 3 files changed, 12 insertions(+), 6 deletions(-) diff -puN include/net/sock.h~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 include/net/sock.h --- a/include/net/sock.h~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 +++ a/include/net/sock.h @@ -745,7 +745,13 @@ static inline int sk_stream_wmem_schedul */ #define sock_owned_by_user(sk) ((sk)->sk_lock.owner) -extern void FASTCALL(lock_sock(struct sock *sk)); +extern void FASTCALL(lock_sock_nested(struct sock *sk, int subclass)); + +static inline void lock_sock(struct sock *sk) +{ + lock_sock_nested(sk, 0); +} + extern void FASTCALL(release_sock(struct sock *sk)); /* BH context may only use the following locking interface. */ diff -puN net/bluetooth/l2cap.c~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 net/bluetooth/l2cap.c --- a/net/bluetooth/l2cap.c~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 +++ a/net/bluetooth/l2cap.c @@ -770,7 +770,7 @@ static int l2cap_sock_accept(struct sock long timeo; int err = 0; - lock_sock(sk); + lock_sock_nested(sk, SINGLE_DEPTH_NESTING); if (sk->sk_state != BT_LISTEN) { err = -EBADFD; @@ -792,7 +792,7 @@ static int l2cap_sock_accept(struct sock release_sock(sk); timeo = schedule_timeout(timeo); - lock_sock(sk); + lock_sock_nested(sk, SINGLE_DEPTH_NESTING); if (sk->sk_state != BT_LISTEN) { err = -EBADFD; diff -puN net/core/sock.c~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 net/core/sock.c --- a/net/core/sock.c~lockdep-annotate-sk_lock-nesting-in-af_bluetooth-v2 +++ a/net/core/sock.c @@ -1527,7 +1527,7 @@ void sock_init_data(struct socket *sock, atomic_set(&sk->sk_refcnt, 1); } -void fastcall lock_sock(struct sock *sk) +void fastcall lock_sock_nested(struct sock *sk, int subclass) { might_sleep(); spin_lock_bh(&sk->sk_lock.slock); @@ -1538,11 +1538,11 @@ void fastcall lock_sock(struct sock *sk) /* * The sk_lock has mutex_lock() semantics here: */ - mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_); + mutex_acquire(&sk->sk_lock.dep_map, subclass, 0, _RET_IP_); local_bh_enable(); } -EXPORT_SYMBOL(lock_sock); +EXPORT_SYMBOL(lock_sock_nested); void fastcall release_sock(struct sock *sk) { _