Hello
On my i.MX6Q based system, loading the rtc-pcf8563 module results in the
following warning. This happens with Linux 4.14 and 4.13.
/ # modprobe rtc-pcf8563
rtc-pcf8563 2-0051: low voltage detected, date/time is not reliable.
rtc-pcf8563 2-0051: rtc core: registered rtc-pcf8563 as rtc0
======================================================
WARNING: possible circular locking dependency detected
4.14.0+ #20 Not tainted
------------------------------------------------------
modprobe/460 is trying to acquire lock:
(i2c_register_adapter){+.+.}, at: [<8045a4b4>]
i2c_adapter_lock_bus+0x14/0x18
but task is already holding lock:
(prepare_lock){+.+.}, at: [<80388254>] clk_prepare_lock+0x14/0xdc
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (prepare_lock){+.+.}:
__mutex_lock+0x58/0x92c
mutex_lock_nested+0x24/0x2c
clk_prepare_lock+0x4c/0xdc
clk_core_get_rate+0x14/0x4c
clk_get_rate+0x1c/0x20
i2c_imx_start+0x20/0x1bc [i2c_imx]
i2c_imx_xfer+0x38/0x990 [i2c_imx]
__i2c_transfer+0x1d0/0x220
i2c_transfer+0x8c/0xbc
i2c_smbus_xfer+0x3c8/0x514
i2c_smbus_read_byte_data+0x3c/0x4c
pca953x_read_single+0x4c/0x80 [gpio_pca953x]
pca953x_gpio_get_direction+0x44/0x7c [gpio_pca953x]
gpiochip_add_data+0x320/0x5d8
devm_gpiochip_add_data+0x40/0x80
pca953x_probe+0x354/0x454 [gpio_pca953x]
i2c_device_probe+0x210/0x268
driver_probe_device+0x160/0x2e0
__driver_attach+0x90/0xb4
bus_for_each_dev+0x74/0x98
driver_attach+0x20/0x28
bus_add_driver+0xd4/0x1e8
driver_register+0xa4/0xe8
i2c_register_driver+0x54/0x80
0x7f068018
do_one_initcall+0xb0/0x158
do_init_module+0x60/0x1c8
load_module+0x198c/0x1eac
SyS_init_module+0x120/0x150
ret_fast_syscall+0x0/0x28
-> #0 (i2c_register_adapter){+.+.}:
lock_acquire+0x78/0x98
rt_mutex_lock+0x38/0x50
i2c_adapter_lock_bus+0x14/0x18
i2c_transfer+0x7c/0xbc
pcf8563_read_block_data+0x68/0x98 [rtc_pcf8563]
pcf8563_clkout_recalc_rate+0x24/0x44 [rtc_pcf8563]
clk_register+0x344/0x538
devm_clk_register+0x3c/0x7c
pcf8563_probe+0x1a8/0x20c [rtc_pcf8563]
i2c_device_probe+0x210/0x268
driver_probe_device+0x160/0x2e0
__driver_attach+0x90/0xb4
bus_for_each_dev+0x74/0x98
driver_attach+0x20/0x28
bus_add_driver+0xd4/0x1e8
driver_register+0xa4/0xe8
i2c_register_driver+0x54/0x80
pcf8563_driver_init+0x18/0x1000 [rtc_pcf8563]
do_one_initcall+0xb0/0x158
do_init_module+0x60/0x1c8
load_module+0x198c/0x1eac
SyS_init_module+0x120/0x150
ret_fast_syscall+0x0/0x28
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(prepare_lock);
lock(i2c_register_adapter);
lock(prepare_lock);
lock(i2c_register_adapter);
*** DEADLOCK ***
3 locks held by modprobe/460:
#0: (&dev->mutex){....}, at: [<803ce808>] __driver_attach+0x68/0xb4
#1: (&dev->mutex){....}, at: [<803ce818>] __driver_attach+0x78/0xb4
#2: (prepare_lock){+.+.}, at: [<80388254>] clk_prepare_lock+0x14/0xdc
stack backtrace:
CPU: 0 PID: 460 Comm: modprobe Not tainted 4.14.0+ #20
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
Backtrace:
[<8010b9f0>] (dump_backtrace) from [<8010bc58>] (show_stack+0x18/0x1c)
r6:00000080 r5:600c0093 r4:00000000 r3:00400100
[<8010bc40>] (show_stack) from [<8056a664>] (dump_stack+0xa0/0xd8)
[<8056a5c4>] (dump_stack) from [<80164340>]
(print_circular_bug+0x278/0x2cc)
r7:ae87e200 r6:80a7f254 r5:80a7f254 r4:80a62c24
[<801640c8>] (print_circular_bug) from [<80162d58>]
(__lock_acquire+0x1104/0x182c)
r10:ae87e7c0 r9:ae2a7aec r8:00000002 r7:ae87e7b8 r6:00000003
r5:ae87e260
r4:ae87e200 r3:ae87e7b8
[<80161c54>] (__lock_acquire) from [<80163bc0>] (lock_acquire+0x78/0x98)
r10:00000000 r9:0000002a r8:7f52662c r7:ae6071e0 r6:00000001
r5:600c0013
r4:00000000
[<80163b48>] (lock_acquire) from [<80581fcc>] (rt_mutex_lock+0x38/0x50)
r6:ae2a7be8 r5:aeaaf824 r4:00000000
[<80581f94>] (rt_mutex_lock) from [<8045a4b4>]
(i2c_adapter_lock_bus+0x14/0x18)
r5:00000002 r4:aeaaf810
[<8045a4a0>] (i2c_adapter_lock_bus) from [<8045acb8>]
(i2c_transfer+0x7c/0xbc)
[<8045ac3c>] (i2c_transfer) from [<7f52624c>]
(pcf8563_read_block_data+0x68/0x98
[rtc_pcf8563])
r6:00000001 r5:ae2a7c27 r4:ae4a6400 r3:ae2a7be7
[<7f5261e4>] (pcf8563_read_block_data [rtc_pcf8563]) from [<7f526650>]
(pcf8563_
clkout_recalc_rate+0x24/0x44 [rtc_pcf8563])
r6:00000000 r5:810d2800 r4:ae5e3800
[<7f52662c>] (pcf8563_clkout_recalc_rate [rtc_pcf8563]) from
[<8038aff0>] (clk_r
egister+0x344/0x538)
[<8038acac>] (clk_register) from [<8038b220>]
(devm_clk_register+0x3c/0x7c)
r9:0000002a r8:7f528020 r7:af76e72c r6:ae4a6420 r5:ae676ad0 r4:ae6071e0
[<8038b1e4>] (devm_clk_register) from [<7f526aa8>]
(pcf8563_probe+0x1a8/0x20c [r
tc_pcf8563])
r6:ae6071d0 r5:ae4a6400 r4:00000000 r3:7f52709c
[<7f526900>] (pcf8563_probe [rtc_pcf8563]) from [<8045b0e4>]
(i2c_device_probe+0
x210/0x268)
r7:ae4a6420 r6:7f528020 r5:7f526900 r4:ae4a6400
[<8045aed4>] (i2c_device_probe) from [<803ce620>]
(driver_probe_device+0x160/0x2
e0)
r8:7f528020 r7:00000000 r6:810d6560 r5:810d6554 r4:ae4a6420 r3:8045aed4
[<803ce4c0>] (driver_probe_device) from [<803ce830>]
(__driver_attach+0x90/0xb4)
r10:810c5808 r9:ae607570 r8:00000000 r7:80929038 r6:7f528020
r5:ae4a6454
r4:ae4a6420 r3:00000000
[<803ce7a0>] (__driver_attach) from [<803cca54>]
(bus_for_each_dev+0x74/0x98)
r6:803ce7a0 r5:7f528020 r4:00000000 r3:00000001
[<803cc9e0>] (bus_for_each_dev) from [<803ce04c>] (driver_attach+0x20/0x28)
r6:ae0e2480 r5:00000000 r4:7f528020
[<803ce02c>] (driver_attach) from [<803cd75c>] (bus_add_driver+0xd4/0x1e8)
[<803cd688>] (bus_add_driver) from [<803cf184>] (driver_register+0xa4/0xe8)
r7:ae607540 r6:ae6078c0 r5:7f52b000 r4:7f528020
[<803cf0e0>] (driver_register) from [<8045a5f8>]
(i2c_register_driver+0x54/0x80)
r5:7f52b000 r4:7f528000
[<8045a5a4>] (i2c_register_driver) from [<7f52b018>]
(pcf8563_driver_init+0x18/0
x1000 [rtc_pcf8563])
r5:7f52b000 r4:7f528080
[<7f52b000>] (pcf8563_driver_init [rtc_pcf8563]) from [<80101c38>]
(do_one_initc
all+0xb0/0x158)
[<80101b88>] (do_one_initcall) from [<801a0e7c>] (do_init_module+0x60/0x1c8)
r8:00000001 r7:ae607540 r6:ae6078c0 r5:00000001 r4:7f528080
[<801a0e1c>] (do_init_module) from [<8019fc7c>] (load_module+0x198c/0x1eac)
r6:7f528080 r5:00000001 r4:ae2a7f30
[<8019e2f0>] (load_module) from [<801a02bc>] (SyS_init_module+0x120/0x150)
r10:00000051 r9:ae2a6000 r8:000c6eb9 r7:00000000 r6:019f8fdc r5:c12d982c
r4:0000582c
[<801a019c>] (SyS_init_module) from [<80107720>] (ret_fast_syscall+0x0/0x28)
r10:00001000 r9:ae2a6000 r8:801078e4 r7:00000080 r6:76f876e0 r5:019f37b0
r4:019d3cf8
