Re: [PATCH v2 net] net: don't omit syncing RX filters to devices that are down

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Mon, Apr 10, 2023 at 10:52:20PM +0300, Vladimir Oltean wrote:
> There are 2 possible ways to solve the issue.
> 
> Alternatively, we could remove the check/optimization and thus make
> dev_mc_del() always propagate down to the ndo_set_rx_mode() of the
> device. This would implicitly solve the IGMP/IGMP6 code paths with DSA,
> as well as any other potential issues of this kind with address deletion
> not being synced prior to device removal.

Self NACK.

After a more careful inspection of dmesg, I now notice this WARN_ON
during probe time:

[    7.710448] mscc_felix 0000:00:00.5 swp0 (uninitialized): PHY [0000:00:00.3:10] driver [Microsemi GE VSC8514 SyncE] (irq=POLL)
[    7.735401]
[    7.736921] ============================================
[    7.742266] WARNING: possible recursive locking detected
[    7.747610] 6.3.0-rc5-01277-g8ec1b4985857 #77 Not tainted
[    7.753048] --------------------------------------------
[    7.758391] kworker/u4:0/8 is trying to acquire lock:
[    7.763477] ffff5c348439a280 (_xmit_ETHER){+...}-{3:3}, at: dev_mc_add+0x40/0xa0
[    7.770991]
[    7.770991] but task is already holding lock:
[    7.776859] ffff5c34843e1280 (_xmit_ETHER){+...}-{3:3}, at: dev_mc_add+0x40/0xa0
[    7.784358]
[    7.784358] other info that might help us debug this:
[    7.790924]  Possible unsafe locking scenario:
[    7.790924]
[    7.796876]        CPU0
[    7.799340]        ----
[    7.801803]   lock(_xmit_ETHER);
[    7.805073]   lock(_xmit_ETHER);
[    7.808342]
[    7.808342]  *** DEADLOCK ***
[    7.808342]
[    7.814295]  May be due to missing lock nesting notation
[    7.814295]
[    7.821119] 7 locks held by kworker/u4:0/8:
[    7.825334]  #0: ffff5c3480007948 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1f8/0x568
[    7.835549]  #1: ffff80000856bd58 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x224/0x568
[    7.844886]  #2: ffff5c34826a71c0 (&dev->mutex){....}-{4:4}, at: __device_attach+0x48/0x1a0
[    7.853358]  #3: ffffb9e51aa8db80 (dsa2_mutex){+.+.}-{4:4}, at: dsa_register_switch+0x50/0x1188
[    7.862182]  #4: ffffb9e51aa70788 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x28/0x40
[    7.869956]  #5: ffff5c34843f95b0 (&idev->mc_lock){+.+.}-{4:4}, at: __ipv6_dev_mc_inc+0xa8/0x498
[    7.878864]  #6: ffff5c34843e1280 (_xmit_ETHER){+...}-{3:3}, at: dev_mc_add+0x40/0xa0
[    7.886803]
[    7.886803] stack backtrace:
[    7.891188] CPU: 1 PID: 8 Comm: kworker/u4:0 Not tainted 6.3.0-rc5-01277-g8ec1b4985857 #77
[    7.904249] Workqueue: events_unbound deferred_probe_work_func
[    7.910146] Call trace:
[    7.912611]  dump_backtrace+0x108/0x130
[    7.916486]  show_stack+0x24/0x30
[    7.919832]  dump_stack_lvl+0x60/0x80
[    7.923531]  dump_stack+0x18/0x28
[    7.926880]  __lock_acquire+0x7e8/0x2fc8
[    7.930850]  lock_acquire+0x118/0x260
[    7.934555]  _raw_spin_lock_nested+0x68/0xb0
[    7.938871]  dev_mc_add+0x40/0xa0
[    7.942218]  dsa_slave_sync_mc+0x68/0x180
[    7.946264]  __hw_addr_sync_dev+0x138/0x158
[    7.950483]  dsa_slave_set_rx_mode+0x3c/0x70
[    7.954796]  __dev_set_rx_mode+0x80/0xa0
[    7.958762]  dev_mc_add+0x74/0xa0
[    7.962109]  igmp6_group_added+0x78/0x128
[    7.966162]  __ipv6_dev_mc_inc+0x278/0x498
[    7.970299]  ipv6_dev_mc_inc+0x20/0x38
[    7.974087]  ipv6_add_dev+0x3f0/0x4d0
[    7.977791]  addrconf_notify+0x1b0/0x4a8
[    7.981757]  raw_notifier_call_chain+0x50/0x88
[    7.986254]  call_netdevice_notifiers+0x74/0xd0
[    7.990823]  register_netdevice+0x4f0/0x600
[    7.995054]  dsa_slave_create+0x3f8/0x620
[    7.999099]  dsa_port_setup+0x10c/0x158
[    8.002978]  dsa_register_switch+0xe18/0x1188
[    8.007378]  felix_pci_probe+0x120/0x1f0
[    8.011345]  pci_device_probe+0x1b0/0x278
[    8.015394]  really_probe+0x13c/0x2f8
[    8.019097]  __driver_probe_device+0xc0/0xf8
[    8.023409]  driver_probe_device+0x48/0x218
[    8.027634]  __device_attach_driver+0x128/0x158
[    8.032209]  bus_for_each_drv+0x12c/0x160
[    8.036257]  __device_attach+0xcc/0x1a0
[    8.040131]  device_initial_probe+0x20/0x38
[    8.044356]  bus_probe_device+0xa0/0x118
[    8.048316]  deferred_probe_work_func+0x98/0xe0
[    8.052890]  process_one_work+0x290/0x568
[    8.056935]  worker_thread+0x238/0x4a8
[    8.060716]  kthread+0x108/0x130
[    8.063983]  ret_from_fork+0x10/0x20

which appears to be a false positive caused by the newly opened time
window in which DSA user ports have net_devices registered, but they
aren't yet upper devices of the DSA master, so their dev->nested_level
is the same.

It seems like I will return to the targeted fix for v3, after some more
investigation here tomorrow.