Lockdep warning after c0feea594e058223973db94c1c32a830c9807c86

sdf
2022-10-12T21:08:21Z

Hi John & Jakub,

Upstream commit c0feea594e05 ("workqueue: don't skip lockdep work
dependency in cancel_work_sync()") seems to trigger the following
lockdep warning during test_prog's sockmap_listen:

[ +0.003631] WARNING: possible circular locking dependency detected
[ +0.003647] 6.0.0-dbx-DEV #10 Not tainted
[ +0.002402] ------------------------------------------------------
[ +0.003685] kworker/1:0/23 is trying to acquire lock:
[ +0.003012] ffff888100b1e3f0 (sk_lock-AF_INET){+.+.}-{0:0}, at:
tcp_sendpage+0x28/0x80
[ +0.004655]
but task is already holding lock:
[ +0.003434] ffff88810642c360 (&psock->work_mutex){+.+.}-{3:3}, at:
sk_psock_backlog+0x2e/0x370
[ +0.005043]
which lock already depends on the new lock.

[ +0.004792]
the existing dependency chain (in reverse order) is:
[ +0.004397]
-> #2 (&psock->work_mutex){+.+.}-{3:3}:
[ +0.003732] __mutex_lock_common+0xdf/0xe70
[ +0.002958] mutex_lock_nested+0x20/0x30
[ +0.002685] sk_psock_backlog+0x2e/0x370
[ +0.002689] process_one_work+0x22c/0x3b0
[ +0.002815] worker_thread+0x21b/0x400
[ +0.002652] kthread+0xf7/0x110
[ +0.002406] ret_from_fork+0x1f/0x30
[ +0.002512]
-> #1 ((work_completion)(&psock->work)){+.+.}-{0:0}:
[ +0.004457] __flush_work+0x6b/0xd0
[ +0.002638] __cancel_work_timer+0x11a/0x1a0
[ +0.002973] cancel_work_sync+0x10/0x20
[ +0.002724] sk_psock_stop+0x298/0x2b0
[ +0.002969] sock_map_close+0xd8/0x140
[ +0.002739] inet_release+0x57/0x80
[ +0.002475] sock_close+0x4b/0xe0
[ +0.002380] __fput+0x101/0x230
[ +0.002347] ____fput+0xe/0x10
[ +0.002259] task_work_run+0x5d/0xb0
[ +0.002535] exit_to_user_mode_loop+0xd6/0xf0
[ +0.003019] exit_to_user_mode_prepare+0xa6/0x100
[ +0.003201] syscall_exit_to_user_mode+0x5b/0x160
[ +0.003145] do_syscall_64+0x49/0x80
[ +0.002549] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ +0.003410]
-> #0 (sk_lock-AF_INET){+.+.}-{0:0}:
[ +0.003906] __lock_acquire+0x16f4/0x30c0
[ +0.002837] lock_acquire+0xc5/0x1c0
[ +0.002599] lock_sock_nested+0x32/0x80
[ +0.002690] tcp_sendpage+0x28/0x80
[ +0.002435] inet_sendpage+0x7b/0xe0
[ +0.002534] kernel_sendpage+0x5d/0xa0
[ +0.002709] skb_send_sock+0x24b/0x2d0
[ +0.002662] sk_psock_backlog+0x106/0x370
[ +0.002908] process_one_work+0x22c/0x3b0
[ +0.002736] worker_thread+0x21b/0x400
[ +0.002552] kthread+0xf7/0x110
[ +0.002252] ret_from_fork+0x1f/0x30
[ +0.002480]
other info that might help us debug this:

[ +0.004778] Chain exists of:
sk_lock-AF_INET --> (work_completion)(&psock->work) -->
&psock->work_mutex

[ +0.007265] Possible unsafe locking scenario:

[ +0.003496] CPU0 CPU1
[ +0.002717] ---- ----
[ +0.002809] lock(&psock->work_mutex);
[ +0.002335]
lock((work_completion)(&psock->work));
[ +0.004496] lock(&psock->work_mutex);
[ +0.003766] lock(sk_lock-AF_INET);
[ +0.002185]
*** DEADLOCK ***

[ +0.003600] 3 locks held by kworker/1:0/23:
[ +0.002698] #0: ffff888100055138 ((wq_completion)events){+.+.}-{0:0},
at: process_one_work+0x1d6/0x3b0
[ +0.005552] #1: ffffc900001e7e58
((work_completion)(&psock->work)){+.+.}-{0:0}, at:
process_one_work+0x1fc/0x3b0
[ +0.006085] #2: ffff88810642c360 (&psock->work_mutex){+.+.}-{3:3}, at:
sk_psock_backlog+0x2e/0x370
[ +0.005424]
stack backtrace:
[ +0.002689] CPU: 1 PID: 23 Comm: kworker/1:0 Not tainted 6.0.0-dbx-DEV #10
[ +0.004086] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ +0.006806] Workqueue: events sk_psock_backlog
[ +0.002699] Call Trace:
[ +0.001577] <TASK>
[ +0.001350] dump_stack_lvl+0x69/0xaa
[ +0.002225] dump_stack+0x10/0x12
[ +0.002051] print_circular_bug+0x289/0x290
[ +0.002531] check_noncircular+0x12c/0x140
[ +0.002578] __lock_acquire+0x16f4/0x30c0
[ +0.002483] ? ret_from_fork+0x1f/0x30
[ +0.002297] ? __this_cpu_preempt_check+0x13/0x20
[ +0.002869] ? lock_is_held_type+0xf8/0x160
[ +0.002511] lock_acquire+0xc5/0x1c0
[ +0.002165] ? tcp_sendpage+0x28/0x80
[ +0.002367] lock_sock_nested+0x32/0x80
[ +0.002401] ? tcp_sendpage+0x28/0x80
[ +0.002262] tcp_sendpage+0x28/0x80
[ +0.002148] inet_sendpage+0x7b/0x[ 12.231432] sysrq: Power Off
e0
[ +0.002202[ 12.234545] kvm: exiting hardware virtualization
] kernel_sendpage+0x5d/0xa0
[ +0.002277] skb_send_sock+0x24b/0x2d0
[ +0.002278] ? _raw_spin_unlock_irqrestore+0x35/0x60
[ +0.003030] ? __this_cpu_preempt_check+0x13/0x20
[ +0.002861] ? lockdep_hardirqs_on+0x97/0x140
[ +0.002685] ? trace_hardirqs_on+0x47/0x50
[ +0.002576] ? _raw_spin_unlock_irqrestore+0x40/0x60
[ +0.003207] sk_psock_backlog+0x106/0x370
[ +0.002476] process_one_work+0x22c/0x3b0
[ +0.002473] worker_thread+0x21b/0x400
[ +0.002335] kthread+0xf7/0x110
[ +0.001954] ? rcu_lock_release+0x20/0x20
[ +0.002444] ? kthread_blkcg+0x30/0x30
[ +0.002325] ret_from_fork+0x1f/0x30
[ +0.002221] </TASK>

This is on bpf-next:

commit d31ada3b511141f4b78cae5a05cc2dad887c40b7 (HEAD -> bpf-next,
bpf-next/master)
Author: David Vernet <void@manifault.com>
Date: Tue Oct 11 11:52:55 2022 -0500

selftests/bpf: Alphabetize DENYLISTs

Are you ware? Any idea what's wrong?
Is there some stable fix I'm missing in bpf-next?