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Date: Thu, 7 Sep 2023 16:03:18 +0200
From: Sascha Hauer <sha@...gutronix.de>
To: netdev@...r.kernel.org
Cc: Andrew Lunn <andrew@...n.ch>, Christian Marangi <ansuelsmth@...il.com>
Subject: possible circular locking dependency in netdev LED trigger
I am very happy that phy LED trigger support is finally merged. Thanks
Andrew and Christion for making this happen :)
I am currently giving the LED support on the dp83867 phy a try. I got
the following log splat when doing a "echo netdev > /sys/class/leds/.../trigger"
on one of the DP83867 provided phy LEDs.
In the netdevice open path we first take &rtnl_mutex in devinet_ioctl()
and afterwards &triggers_list_lock in led_trigger_register().
The other path takes the locks in the opposite order: First it takes
&triggers_list_lock first in led_trigger_write() and then &rtnl_mutex
in register_netdevice_notifier(), so a classical ABBA deadlock. At least
that's what I see from looking at the code, I am a bit confused by the
lockdep output.
Any idea how we can solve this?
Sascha
-------------------------------8<---------------------------------------
[ 53.942317] ======================================================
[ 53.948607] WARNING: possible circular locking dependency detected
[ 53.954898] 6.5.0-11704-g3f86ed6ec0b3 #367 Not tainted
[ 53.960136] ------------------------------------------------------
[ 53.966426] sh/579 is trying to acquire lock:
[ 53.970872] ffff800082354af8 (pernet_ops_rwsem){+.+.}-{4:4}, at: register_netdevice_notifier+0x30/0x12c
[ 53.980539]
[ 53.980539] but task is already holding lock:
[ 53.986485] ffff000004f2de68 (&led_cdev->trigger_lock){+.+.}-{4:4}, at: led_trigger_write+0x100/0x14c
[ 53.995959]
[ 53.995959] which lock already depends on the new lock.
[ 53.995959]
[ 54.004282]
[ 54.004282] the existing dependency chain (in reverse order) is:
[ 54.011898]
[ 54.011898] -> #3 (&led_cdev->trigger_lock){+.+.}-{4:4}:
[ 54.018877] down_write+0x5c/0x120
[ 54.022911] led_trigger_set_default+0x40/0xd0
[ 54.028001] led_classdev_register_ext+0x2b8/0x3c8
[ 54.033442] __sdhci_add_host+0x1e4/0x368
[ 54.038083] sdhci_add_host+0x3c/0x50
[ 54.042375] sdhci_arasan_probe+0x9dc/0xaa4
[ 54.047191] platform_probe+0x68/0xc4
[ 54.051481] really_probe+0x148/0x2ac
[ 54.055768] __driver_probe_device+0x78/0x12c
[ 54.060759] driver_probe_device+0xd8/0x160
[ 54.065574] __device_attach_driver+0xb8/0x138
[ 54.070657] bus_for_each_drv+0x80/0xdc
[ 54.075118] __device_attach_async_helper+0xb0/0xd4
[ 54.080635] async_run_entry_fn+0x34/0xe0
[ 54.085274] process_one_work+0x1ec/0x51c
[ 54.089920] worker_thread+0x1ec/0x3e4
[ 54.094300] kthread+0x120/0x124
[ 54.098147] ret_from_fork+0x10/0x20
[ 54.102343]
[ 54.102343] -> #2 (triggers_list_lock){++++}-{4:4}:
[ 54.108880] down_write+0x5c/0x120
[ 54.112915] led_trigger_register+0x50/0x1b4
[ 54.117822] phy_led_triggers_register+0xa4/0x244
[ 54.123167] phy_attach_direct+0x158/0x378
[ 54.127906] phylink_fwnode_phy_connect+0x8c/0x10c
[ 54.133331] phylink_of_phy_connect+0x1c/0x28
[ 54.138316] macb_phylink_connect+0x48/0x120
[ 54.143220] macb_open+0x214/0x34c
[ 54.147235] __dev_open+0x100/0x1e0
[ 54.151351] __dev_change_flags+0x19c/0x21c
[ 54.156167] dev_change_flags+0x24/0x6c
[ 54.160632] devinet_ioctl+0x488/0x7d8
[ 54.165007] inet_ioctl+0x1e8/0x1f8
[ 54.169117] sock_do_ioctl+0x48/0xf8
[ 54.173317] sock_ioctl+0x250/0x374
[ 54.177433] __arm64_sys_ioctl+0xac/0xf0
[ 54.181989] invoke_syscall+0x48/0x114
[ 54.186370] el0_svc_common.constprop.0+0xc0/0xe0
[ 54.191719] do_el0_svc+0x1c/0x28
[ 54.195660] el0_svc+0x58/0x114
[ 54.199413] el0t_64_sync_handler+0x100/0x12c
[ 54.204403] el0t_64_sync+0x190/0x194
[ 54.208685]
[ 54.208685] -> #1 (rtnl_mutex){+.+.}-{4:4}:
[ 54.214515] __mutex_lock+0xa0/0x7b0
[ 54.218717] mutex_lock_nested+0x24/0x30
[ 54.223270] rtnl_lock+0x1c/0x28
[ 54.227115] register_netdevice_notifier+0x38/0x12c
[ 54.232640] rtnetlink_init+0x2c/0x50c
[ 54.237016] netlink_proto_init+0x148/0x1e0
[ 54.241832] do_one_initcall+0x74/0x2f8
[ 54.246287] kernel_init_freeable+0x290/0x4d0
[ 54.251278] kernel_init+0x24/0x1dc
[ 54.255389] ret_from_fork+0x10/0x20
[ 54.259581]
[ 54.259581] -> #0 (pernet_ops_rwsem){+.+.}-{4:4}:
[ 54.265943] __lock_acquire+0x1358/0x1f64
[ 54.270578] lock_acquire+0x1ec/0x30c
[ 54.274860] down_write+0x5c/0x120
[ 54.278893] register_netdevice_notifier+0x30/0x12c
[ 54.284426] netdev_trig_activate+0x178/0x1dc
[ 54.289418] led_trigger_set+0x130/0x260
[ 54.293978] led_trigger_write+0x10c/0x14c
[ 54.298709] sysfs_kf_bin_write+0x68/0x88
[ 54.303353] kernfs_fop_write_iter+0x120/0x1b0
[ 54.308437] vfs_write+0x194/0x2a8
[ 54.312458] ksys_write+0x6c/0x100
[ 54.316477] __arm64_sys_write+0x1c/0x28
[ 54.321024] invoke_syscall+0x48/0x114
[ 54.325405] el0_svc_common.constprop.0+0xc0/0xe0
[ 54.330756] do_el0_svc+0x1c/0x28
[ 54.334695] el0_svc+0x58/0x114
[ 54.338451] el0t_64_sync_handler+0x100/0x12c
[ 54.343442] el0t_64_sync+0x190/0x194
[ 54.347721]
[ 54.347721] other info that might help us debug this:
[ 54.347721]
[ 54.355873] Chain exists of:
[ 54.355873] pernet_ops_rwsem --> triggers_list_lock --> &led_cdev->trigger_lock
[ 54.355873]
[ 54.367981] Possible unsafe locking scenario:
[ 54.367981]
[ 54.374013] CPU0 CPU1
[ 54.378633] ---- ----
[ 54.383251] lock(&led_cdev->trigger_lock);
[ 54.387629] lock(triggers_list_lock);
[ 54.394126] lock(&led_cdev->trigger_lock);
[ 54.401056] lock(pernet_ops_rwsem);
[ 54.404827]
[ 54.404827] *** DEADLOCK ***
[ 54.404827]
[ 54.410856] 6 locks held by sh/579:
[ 54.414425] #0: ffff00000549f418 (sb_writers#5){.+.+}-{0:0}, at: vfs_write+0xa4/0x2a8
[ 54.422598] #1: ffff000007e90890 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0xf0/0x1b0
[ 54.431637] #2: ffff000004f69f28 (kn->active#39){.+.+}-{0:0}, at: kernfs_fop_write_iter+0xf8/0x1b0
[ 54.440963] #3: ffff000004f2df70 (&led_cdev->led_access){+.+.}-{4:4}, at: led_trigger_write+0x3c/0x14c
[ 54.450629] #4: ffff800082340c08 (triggers_list_lock){++++}-{4:4}, at: led_trigger_write+0x94/0x14c
[ 54.460026] #5: ffff000004f2de68 (&led_cdev->trigger_lock){+.+.}-{4:4}, at: led_trigger_write+0x100/0x14c
[ 54.469953]
[ 54.469953] stack backtrace:
[ 54.474405] CPU: 1 PID: 579 Comm: sh Not tainted 6.5.0-11704-g3f86ed6ec0b3 #367
[ 54.481865] Hardware name: Wolfvision ZynqMP PF4 (DT)
[ 54.487012] Call trace:
[ 54.489520] dump_backtrace+0x98/0xf0
[ 54.493276] show_stack+0x18/0x24
[ 54.496674] dump_stack_lvl+0x60/0xac
[ 54.500429] dump_stack+0x18/0x24
[ 54.503826] print_circular_bug+0x284/0x364
[ 54.508108] check_noncircular+0x158/0x16c
[ 54.512299] __lock_acquire+0x1358/0x1f64
[ 54.516405] lock_acquire+0x1ec/0x30c
[ 54.520158] down_write+0x5c/0x120
[ 54.523662] register_netdevice_notifier+0x30/0x12c
[ 54.528665] netdev_trig_activate+0x178/0x1dc
[ 54.533127] led_trigger_set+0x130/0x260
[ 54.537158] led_trigger_write+0x10c/0x14c
[ 54.541361] sysfs_kf_bin_write+0x68/0x88
[ 54.545474] kernfs_fop_write_iter+0x120/0x1b0
[ 54.550029] vfs_write+0x194/0x2a8
[ 54.553521] ksys_write+0x6c/0x100
[ 54.557008] __arm64_sys_write+0x1c/0x28
[ 54.561028] invoke_syscall+0x48/0x114
[ 54.564878] el0_svc_common.constprop.0+0xc0/0xe0
[ 54.569701] do_el0_svc+0x1c/0x28
[ 54.573110] el0_svc+0x58/0x114
[ 54.576337] el0t_64_sync_handler+0x100/0x12c
[ 54.580798] el0t_64_sync+0x190/0x194
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