[tipc-discussion] [PATCH net-next v2 3/6] tipc: add lock nesting notation to quiet lockdep warning

[Ying X. <yin...@wi...>]

Add lock nesting notation to quiet the following lockdep warning:

[ INFO: possible recursive locking detected ]
---------------------------------------------
kworker/u:0/6 is trying to acquire lock:
(sk_lock-AF_TIPC){+.+.+.}, at: [<c8c1226c>] accept+0x15c/0x310 [tipc]

but task is already holding lock:
(sk_lock-AF_TIPC){+.+.+.}, at: [<c8c12138>] accept+0x28/0x310 [tipc]

other info that might help us debug this:
Possible unsafe locking scenario:

        CPU0
        ----
        lock(sk_lock-AF_TIPC);
        lock(sk_lock-AF_TIPC);

        *** DEADLOCK ***

May be due to missing lock nesting notation
3 locks held by kworker/u:0/6:

stack backtrace:
Pid: 6, comm: kworker/u:0 Not tainted 3.5.0+ #25
Call Trace:
[<c1092883>] print_deadlock_bug+0xe3/0xf0
[<c1094472>] validate_chain+0x5b2/0x720
[<c109485a>] __lock_acquire+0x27a/0x460
[<c1094ad0>] lock_acquire+0x90/0x100
[<c8c1226c>] ? accept+0x15c/0x310 [tipc]
[<c1489d10>] lock_sock_nested+0x70/0x90
[<c8c1226c>] ? accept+0x15c/0x310 [tipc]
[<c8c1226c>] accept+0x15c/0x310 [tipc]
[<c1587962>] ? _raw_spin_unlock+0x22/0x30
[<c1486f51>] ? sock_create_lite+0x71/0x90
[<c1486fbb>] kernel_accept+0x4b/0x90
[<c8c13619>] tipc_accept_from_sock+0x29/0xa0 [tipc]
[<c8c13115>] tipc_recv_work+0x15/0x30 [tipc]
[<c1054c6c>] process_one_work+0x1cc/0x4a0
[<c1054bf0>] ? process_one_work+0x150/0x4a0
[<c8c13100>] ? tipc_close_conn+0xa0/0xa0 [tipc]
[<c1056c92>] worker_thread+0x102/0x350
[<c109382b>] ? trace_hardirqs_on+0xb/0x10
[<c1056b90>] ? manage_workers+0x100/0x100
[<c105b614>] kthread+0x84/0x90
[<c105b590>] ? __init_kthread_worker+0x60/0x60
[<c158ed62>] kernel_thread_helper+0x6/0x10

Signed-off-by: Ying Xue <yin...@wi...>
---
 net/tipc/socket.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 2a5ccdf..6395560 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1510,7 +1510,7 @@ static int accept(struct socket *sock, struct socket *new_sock, int flags)
 		u32 new_ref = new_tport->ref;
 		struct tipc_msg *msg = buf_msg(buf);
 
-		lock_sock(new_sk);
+		lock_sock_nested(new_sk, SINGLE_DEPTH_NESTING);
 
 		/*
 		 * Reject any stray messages received by new socket
-- 
1.7.1