btbcm: possible circular locking dependency linux-next-20180327
Peter Robinson
pbrobinson at gmail.com
Sat Mar 31 06:16:26 PDT 2018
On Sat, Mar 31, 2018 at 12:49 PM, Stefan Wahren <stefan.wahren at i2se.com> wrote:
> Hi,
>
> i build linux-next-20180327 with bcm2835_defconfig, but additionally enabled the following settings:
>
> CONFIG_SMP=y
> CONFIG_PREEMPT=y
> CONFIG_PROVE_LOCKING=y
>
> If i boot my RPi Zero W, then i will get the following output during hci_uart probe:
I saw something similar, sorry don't have the exact bits close to
hand, on the RPI3 on 4.16 when I applied the this patch [1],
unfortunately I never got enough time to go back and debug it further.
The description in the patch is a bit misleading too as it mentions
it's specifically for the Zero W but applies the changes to
thebcm283x.dtsi which affects all editions of the RPi.
Peter
[1] https://patchwork.kernel.org/patch/10240919/
> [ 42.245521] ======================================================
> [ 42.265953] WARNING: possible circular locking dependency detected
> [ 42.286527] 4.16.0-rc7-next-20180327+ #2 Tainted: G C
> [ 42.307153] ------------------------------------------------------
> [ 42.327529] kworker/u2:1/31 is trying to acquire lock:
> [ 42.346819] (bcm_device_lock){+.+.}, at: [<bf07b028>] bcm_recv+0xa4/0x10c [hci_uart]
> [ 42.369028]
> but task is already holding lock:
> [ 42.402020] (&buf->lock){+.+.}, at: [<c04ad460>] flush_to_ldisc+0x2c/0xc0
> [ 42.422713]
> which lock already depends on the new lock.
>
> [ 42.471181]
> the existing dependency chain (in reverse order) is:
> [ 42.505116]
> -> #3 (&buf->lock){+.+.}:
> [ 42.536142] __763608] __ldsem_down_write_nested+0x4c/0x280
> [ 42.780869] ldsem_down_write+0x3c/0x48
> [ 42.797163] tty_ldisc_lock+0x20/0x44
> [ 42.813230] tty_init_dev+0xd8/0x1b0
> [ 42.829130] tty_open+0x30c/0x32c
> [ 42.844633] chrdev_open+0x154/0x170
> [ 42.860303] do_dentry_open.constprop.4+0x2a8/0x320
> [ 42.877260] vfs_open+0x78/0x7c
> [ 42.892198] path_openat+0xc14/0xde0
> [ 42.907367] do_filp_open+0x40/0x8c
> [ 42.922270] do_sys_open+0x114/0x1c4
> [ 42.937142] kernel_init_freeable+0x12c/0x1e0
> [ 42.952797] kernel_init+0x18/0x120
> [ 42.967461] ret_from_fork+0x14/0x20
> [ 42.982195] (null)
> [ 42.995444]
> -> #1 (&tty->legacy_mutex){+.+.}:
> [ 43.022015] __mutex_lock+0x70/0x9b4
> [ 43.036665] mutex_lock_nested+0x2c/0x34
> [ 43.051661] tty_lock+0x5c/0x6c
> [ 43.065808] tty_init_dev+0x4c/0x1b0
> [ 43.080298] ttyport_open+0x34/0x14c
> [ 43.094701] serdev_device_open+0x34/0x40
> [ 43.109685] bcm_open+0x9c/0x190 [hci_uart]
> [ 43.124862] hci_uart_register_device+0x48/0x228 [hci_uart]
> [ 43.141536] bcm_serdev_probe+0xac/0xcc [hci_uart]
> [ 43.157381] serdev_drv_probe+0x20/0x24
> [ 43.172165] driver_probe_device+0x2d4/0x46c
> [ 43.187363] __driver_attach+0x98/0x108
> [ 43.202081] bus_for_each_dev+0x68/0x8c
> [ 43.216802] driver_attach+0x28/0x30
> [ 43.231232] driver_attach_async+0x20/0x58
> [ 43.246142] async_run_entry_fn+0x98/0x1a0
> [ 43.261105] process_one_work+0x3c8/0x76c
> [ 43.276054] worker_thread+0x2b0/0x43c
> [ 43.290632] kthread+0x158/0x174
> [ 43.304530] ret_from_fork+0x14/0x20
> [ 43.318693] (null)
> [ 43.331378]
> -> #0 (bcm_device_lock){+.+.}:
> [ 43.356310] lock_acquire+0x228/0x298
> [ 43.370173] __mutex_lock+0x70/0x9b4
> [ 43.383785] mutex_lock_nested+0x2c/0x34
> [ 43.397711] bcm_recv+0xa4/0x10c [hci_uart]
> [ 43.411957] hci_uart_receive_buf+0x68/0x84 [hci_uart]
> [ 43.427034] ttyport_receive_buf+0x6c/0xe4
> [ 43.440958] flush_to_ldisc+0xa0/0xc0
> [ 43.454321] process_one_work+0x3c8/0x76c
> [ 43.468099] worker_thread+0x2b0/0x43c
> [ 43.481666] kthread+0x158/0x174
> [ 43.494633] ret_from_fork+0x14/0x20
> [ 43.507831] (null)
> [ 43.519665]
> other info that might help us debug this:
>
> [ 43.554302] Chain exists of:
> bcm_device_lock --> &tty->ldisc_sem --> &buf->lock
>
> [ 43.591776] Possible unsafe locking scenario:
>
> [ 43.615986] CPU0 CPU1
> [ 43.629708] ---- ----
> [ 43.643463] lock(&buf->lock);
> [ 43.655748] lock(&tty->ldisc_sem);
> [ 43.671197] lock(&buf->lock);
> [ 43.686220] lock(bcm_device_lock);
> [ 43.699078]
> *** DEADLOCK ***
>
> [ 43.731942] 3 locks held by kworker/u2:1/31:
> [ 43.745364] #0: ((wq_completion)"events_unbound"){+.+.}, at: [<c013fb3c>] process_one_work+0x1e0/0x76c
> [ 43.764636] #1: ((work_completion)(&buf->work)){+.+.}, at: [<c013fb3c>] process_one_work+0x1e0/0x76c
> [ 43.783902] #2: (&buf->lock){+.+.}, at: [<c04ad460>] flush_to_ldisc+0x2c/0xc0
> [ 43.801205]
> stack backtrace:
> [ 43.824860] CPU: 0 PID: 31 Comm: kworker/u2:1 Tainted: G C 4.16.0-rc7-next-20180327+ #2
> [ 43.844393] Hardware name: BCM2835
> [ 43.857885] Workqueue: events_unbound flush_to_ldisc
> [ 43.873103] [<c01118f4>] (unwind_backtrace) from [<c010da50>] (show_stack+0x20/0x24)
> [ 43.891391] [<c010da50>] (show_stack) from [<c08f3590>] (dump_stack+0xa4/0xe0)
> [ 43.909283] [<c08f3590>] (dump_stack) from [<c017d4e0>] (print_circular_bug.constprop.20+0x1dc/0x2d8)
> [ 43.929391] [<c017d4e0>] (print_circular_bug.constprop.20) from [<c017fd30>] (__lock_acquire+0xf00/0x172c)
> [ 43.950197] [<c017fd30>] (__lock_acquire) from [<c0180ff8>] (lock_acquire+0x228/0x298)
> [ 43.969314] [<c0180ff8>] (lock_acquire) from [<c0909a40>] (__mutex_lock+0x70/0x9b4)
> [ 43.988308] [<c0909a40>] (__mutex_lock) from [<c090a3b0>] (mutex_lock_nested+0x2c/0x34)
> [ 44.007837] [<c090a3b0>] (mutex_lock_nested) from [<bf07b028>] (bcm_recv+0xa4/0x10c [hci_uart])
> [ 44.028328] [<bf07b028>] (bcm_recv [hci_uart]) from [<bf079bf8>] (hci_uart_receive_buf+0x68/0x84 [hci_uart])
> [ 44.050162] [<bf079bf8>] (hci_uart_receive_buf [hci_uart]) from [<c04cf928>] (ttyport_receive_buf+0x6c/0xe4)
> [ 44.072188] [<c04cf928>] (ttyport_receive_buf) from [<c04ad4d4>] (flush_to_ldisc+0xa0/0xc0)
> [ 44.092841] [<c04ad4d4>] (flush_to_ldisc) from [<c013fd24>] (process_one_work+0x3c8/0x76c)
> [ 44.113440] [<c013fd24>] (process_one_work) from [<c01414d0>] (worker_thread+0x2b0/0x43c)
> [ 44.134095] [<c01414d0>] (worker_thread) from [<c0146fa4>] (kthread+0x158/0x174)
> [ 44.153985] [<c0146fa4>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
> [ 44.173718] Exception stack(0xd8fcdfb0 to 0xd8fcdff8)
> [ 44.191211] dfa0: 00000000 00000000 00000000 00000000
> [ 44.212185] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 44.233216] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>
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