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SubjectRE: net/tipc: recursive locking in tipc_link_reset
Date
Hi Dmitry,
Yes, we are aware of this, the kernel test robot warned us about this a few days ago.
I am looking into it.

///jon

> -----Original Message-----
> From: Dmitry Vyukov <dvyukov@google.com>
> Sent: October 11, 2018 3:55 AM
> To: parthasarathy.bhuvaragan@ericsson.com; Jon Maloy
> <jon.maloy@ericsson.com>; David Miller <davem@davemloft.net>; Ying Xue
> <ying.xue@windriver.com>; netdev <netdev@vger.kernel.org>; tipc-
> discussion@lists.sourceforge.net; LKML <linux-kernel@vger.kernel.org
> Subject: net/tipc: recursive locking in tipc_link_reset
>
> Hi,
>
> I am getting the following error while booting the latest kernel on
> bb2d8f2f61047cbde08b78ec03e4ebdb01ee5434 (Oct 10). Config is attached.
>
> Since this happens during boot, this makes LOCKDEP completely unusable,
> does not allow to discover any other locking issues and masks all new bugs
> being introduced into kernel.
> Please fix asap.
> Thanks
>
>
> WARNING: possible recursive locking detected 4.19.0-rc7+ #14 Not tainted
> --------------------------------------------
> swapper/0/1 is trying to acquire lock:
> 00000000dcfc0fc8 (&(&list->lock)->rlock#4){+...}, at: spin_lock_bh
> include/linux/spinlock.h:334 [inline]
> 00000000dcfc0fc8 (&(&list->lock)->rlock#4){+...}, at:
> tipc_link_reset+0x125/0xdf0 net/tipc/link.c:850
>
> but task is already holding lock:
> 00000000cbb9b036 (&(&list->lock)->rlock#4){+...}, at: spin_lock_bh
> include/linux/spinlock.h:334 [inline]
> 00000000cbb9b036 (&(&list->lock)->rlock#4){+...}, at:
> tipc_link_reset+0xfa/0xdf0 net/tipc/link.c:849
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&(&list->lock)->rlock#4);
> lock(&(&list->lock)->rlock#4);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 2 locks held by swapper/0/1:
> #0: 00000000f7539d34 (pernet_ops_rwsem){+.+.}, at:
> register_pernet_subsys+0x19/0x40 net/core/net_namespace.c:1051
> #1: 00000000cbb9b036 (&(&list->lock)->rlock#4){+...}, at:
> spin_lock_bh include/linux/spinlock.h:334 [inline]
> #1: 00000000cbb9b036 (&(&list->lock)->rlock#4){+...}, at:
> tipc_link_reset+0xfa/0xdf0 net/tipc/link.c:849
>
> stack backtrace:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.0-rc7+ #14 Hardware name:
> QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1af/0x295 lib/dump_stack.c:113 print_deadlock_bug
> kernel/locking/lockdep.c:1759 [inline] check_deadlock
> kernel/locking/lockdep.c:1803 [inline] validate_chain
> kernel/locking/lockdep.c:2399 [inline]
> __lock_acquire+0xf1e/0x3c60 kernel/locking/lockdep.c:3411
> lock_acquire+0x1db/0x520 kernel/locking/lockdep.c:3900
> __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
> _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh
> include/linux/spinlock.h:334 [inline]
> tipc_link_reset+0x125/0xdf0 net/tipc/link.c:850
> tipc_link_bc_create+0xb5/0x1f0 net/tipc/link.c:526
> tipc_bcast_init+0x59b/0xab0 net/tipc/bcast.c:521
> tipc_init_net+0x472/0x610 net/tipc/core.c:82
> ops_init+0xf7/0x520 net/core/net_namespace.c:129
> __register_pernet_operations net/core/net_namespace.c:940 [inline]
> register_pernet_operations+0x453/0xac0 net/core/net_namespace.c:1011
> register_pernet_subsys+0x28/0x40 net/core/net_namespace.c:1052
> tipc_init+0x83/0x104 net/tipc/core.c:140 do_one_initcall+0x109/0x70a
> init/main.c:885 do_initcall_level init/main.c:953 [inline] do_initcalls
> init/main.c:961 [inline] do_basic_setup init/main.c:979 [inline]
> kernel_init_freeable+0x4bd/0x57f init/main.c:1144
> kernel_init+0x13/0x180 init/main.c:1063
> ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
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