Hi Cong, Taehee,
On Mon, 4 May 2020 at 21:45, Taehee Yoo <ap420...@gmail.com> wrote:
>
> On Sun, 3 May 2020 at 14:22, Cong Wang <xiyou.wangc...@gmail.com> wrote:
> >
>
> Hi Cong,
> Thank you for this work!
>
> > This patch reverts the folowing commits:
> >
> > commit 064ff66e2bef84f1153087612032b5b9eab005bd
> > "bonding: add missing netdev_update_lockdep_key()"
> >
> > commit 53d374979ef147ab51f5d632dfe20b14aebeccd0
> > "net: avoid updating qdisc_xmit_lock_key in netdev_update_lockdep_key()"
> >
> > commit 1f26c0d3d24125992ab0026b0dab16c08df947c7
> > "net: fix kernel-doc warning in <linux/netdevice.h>"
> >
> > commit ab92d68fc22f9afab480153bd82a20f6e2533769
> > "net: core: add generic lockdep keys"
> >
> > but keeps the addr_list_lock_key because we still lock
> > addr_list_lock nestedly on stack devices, unlikely xmit_lock
> > this is safe because we don't take addr_list_lock on any fast
> > path.
> >
> > Reported-and-tested-by:
> > syzbot+aaa6fa4949cc5d9b7...@syzkaller.appspotmail.com
> > Cc: Dmitry Vyukov <dvyu...@google.com>
> > Cc: Taehee Yoo <ap420...@gmail.com>
> > Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
>
> Acked-by: Taehee Yoo <ap420...@gmail.com>
>
> Thank you,
> Taehee Yoo
I have a platform with the following layout:
Regular NIC
|
+----> DSA master for switch port
|
+----> DSA master for another switch port
After changing DSA back to static lockdep class keys, I get this splat:
[ 13.361198] ============================================
[ 13.366524] WARNING: possible recursive locking detected
[ 13.371851] 5.7.0-rc4-02121-gc32a05ecd7af-dirty #988 Not tainted
[ 13.377874] --------------------------------------------
[ 13.383201] swapper/0/0 is trying to acquire lock:
[ 13.388004] ffff0000668ff298
(&dsa_slave_netdev_xmit_lock_key){+.-.}-{2:2}, at:
__dev_queue_xmit+0x84c/0xbe0
[ 13.397879]
[ 13.397879] but task is already holding lock:
[ 13.403727] ffff0000661a1698
(&dsa_slave_netdev_xmit_lock_key){+.-.}-{2:2}, at:
__dev_queue_xmit+0x84c/0xbe0
[ 13.413593]
[ 13.413593] other info that might help us debug this:
[ 13.420140] Possible unsafe locking scenario:
[ 13.420140]
[ 13.426075] CPU0
[ 13.428523] ----
[ 13.430969] lock(&dsa_slave_netdev_xmit_lock_key);
[ 13.435946] lock(&dsa_slave_netdev_xmit_lock_key);
[ 13.440924]
[ 13.440924] *** DEADLOCK ***
[ 13.440924]
[ 13.446860] May be due to missing lock nesting notation
[ 13.446860]
[ 13.453668] 6 locks held by swapper/0/0:
[ 13.457598] #0: ffff800010003de0
((&idev->mc_ifc_timer)){+.-.}-{0:0}, at: call_timer_fn+0x0/0x400
[ 13.466593] #1: ffffd4d3fb478700 (rcu_read_lock){....}-{1:2}, at:
mld_sendpack+0x0/0x560
[ 13.474803] #2: ffffd4d3fb478728 (rcu_read_lock_bh){....}-{1:2},
at: ip6_finish_output2+0x64/0xb10
[ 13.483886] #3: ffffd4d3fb478728 (rcu_read_lock_bh){....}-{1:2},
at: __dev_queue_xmit+0x6c/0xbe0
[ 13.492793] #4: ffff0000661a1698
(&dsa_slave_netdev_xmit_lock_key){+.-.}-{2:2}, at:
__dev_queue_xmit+0x84c/0xbe0
[ 13.503094] #5: ffffd4d3fb478728 (rcu_read_lock_bh){....}-{1:2},
at: __dev_queue_xmit+0x6c/0xbe0
[ 13.512000]
[ 13.512000] stack backtrace:
[ 13.516369] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
5.7.0-rc4-02121-gc32a05ecd7af-dirty #988
[ 13.530421] Call trace:
[ 13.532871] dump_backtrace+0x0/0x1d8
[ 13.536539] show_stack+0x24/0x30
[ 13.539862] dump_stack+0xe8/0x150
[ 13.543271] __lock_acquire+0x1030/0x1678
[ 13.547290] lock_acquire+0xf8/0x458
[ 13.550873] _raw_spin_lock+0x44/0x58
[ 13.554543] __dev_queue_xmit+0x84c/0xbe0
[ 13.558562] dev_queue_xmit+0x24/0x30
[ 13.562232] dsa_slave_xmit+0xe0/0x128
[ 13.565988] dev_hard_start_xmit+0xf4/0x448
[ 13.570182] __dev_queue_xmit+0x808/0xbe0
[ 13.574200] dev_queue_xmit+0x24/0x30
[ 13.577869] neigh_resolve_output+0x15c/0x220
[ 13.582237] ip6_finish_output2+0x244/0xb10
[ 13.586430] __ip6_finish_output+0x1dc/0x298
[ 13.590709] ip6_output+0x84/0x358
[ 13.594116] mld_sendpack+0x2bc/0x560
[ 13.597786] mld_ifc_timer_expire+0x210/0x390
[ 13.602153] call_timer_fn+0xcc/0x400
[ 13.605822] run_timer_softirq+0x588/0x6e0
[ 13.609927] __do_softirq+0x118/0x590
[ 13.613597] irq_exit+0x13c/0x148
[ 13.616918] __handle_domain_irq+0x6c/0xc0
[ 13.621023] gic_handle_irq+0x6c/0x160
[ 13.624779] el1_irq+0xbc/0x180
[ 13.627927] cpuidle_enter_state+0xb4/0x4d0
[ 13.632120] cpuidle_enter+0x3c/0x50
[ 13.635703] call_cpuidle+0x44/0x78
[ 13.639199] do_idle+0x228/0x2c8
[ 13.642433] cpu_startup_entry+0x2c/0x48
[ 13.646363] rest_init+0x1ac/0x280
[ 13.649773] arch_call_rest_init+0x14/0x1c
[ 13.653878] start_kernel+0x490/0x4bc
Unfortunately I can't really test DSA behavior prior to patch
ab92d68fc22f ("net: core: add generic lockdep keys"), because in
October, some of these DSA drivers were not in mainline.
Also I don't really have a clear idea of how nesting should be
signalled to lockdep.
Do you have any suggestion what might be wrong?
Thanks,
-Vladimir
