From: Ying Xue Date: Mon, 3 Dec 2012 08:12:07 +0000 (+0800) Subject: tipc: add lock nesting notation to quiet lockdep warning X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=258f8667a29d72b1c220065632b39c0faeb061ca;p=linux-beck.git tipc: add lock nesting notation to quiet lockdep warning TIPC accept() call grabs the socket lock on a newly allocated socket while holding the socket lock on an old socket. But lockdep worries that this might be a recursive lock attempt: [ INFO: possible recursive locking detected ] --------------------------------------------- kworker/u:0/6 is trying to acquire lock: (sk_lock-AF_TIPC){+.+.+.}, at: [] accept+0x15c/0x310 [tipc] but task is already holding lock: (sk_lock-AF_TIPC){+.+.+.}, at: [] 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 [...] Tell lockdep that this locking is safe by using lock_sock_nested(). This is similar to what was done in commit 5131a184a3458d9 for SCTP code ("SCTP: lock_sock_nested in sctp_sock_migrate"). Also note that this is isn't something that is seen normally, as it was uncovered with some experimental work-in-progress code not yet ready for mainline. So no need for stable backports or similar of this commit. Signed-off-by: Ying Xue Signed-off-by: Paul Gortmaker --- diff --git a/net/tipc/socket.c b/net/tipc/socket.c index ef75b6270247..b5c9795cf151 100644 --- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -1543,7 +1543,8 @@ 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); + /* we lock on new_sk; but lockdep sees the lock on sk */ + lock_sock_nested(new_sk, SINGLE_DEPTH_NESTING); /* * Reject any stray messages received by new socket