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Message-ID:
<VI2PR04MB11147CCEFE4204B852807AAF2E841A@VI2PR04MB11147.eurprd04.prod.outlook.com>
Date: Tue, 1 Jul 2025 03:16:08 +0000
From: Carlos Song <carlos.song@....com>
To: "mturquette@...libre.com" <mturquette@...libre.com>, "sboyd@...nel.org"
<sboyd@...nel.org>, "rafael@...nel.org" <rafael@...nel.org>,
"pavel@...nel.org" <pavel@...nel.org>, "len.brown@...el.com"
<len.brown@...el.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"dakr@...nel.org" <dakr@...nel.org>, Aisheng Dong <aisheng.dong@....com>,
Andi Shyti <andi.shyti@...nel.org>, "shawnguo@...nel.org"
<shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>, "festevam@...il.com"
<festevam@...il.com>, Frank Li <frank.li@....com>
CC: "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-i2c@...r.kernel.org"
<linux-i2c@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Bough Chen
<haibo.chen@....com>, Jun Li <jun.li@....com>
Subject: Dead lock with clock global prepare_lock mutex and device's
power.runtime_status
Hi, All:
We met the dead lock issue recently and think it should be common issue and not sure how to fix it.
We use gpio-gate-clock clock provider (drivers/clk/clk-gpio.c), gpio is one of i2c gpio expander (drivers/gpio/gpio-pcf857x.c). Our i2c driver enable run time pm (drivers/i2c/busses/i2c-imx-lpi2c.c [1]). System random blocked when at reboot.
The dead lock happen as below call stacks
Task 117 Task 120
schedule()
clk_prepare_lock()--> wait prepare_lock(mutex_lock) schedule() wait for power.runtime_status exit RPM_SUSPENDING
^^^^ A ^^^^ B
clk_bulk_unprepare() rpm_resume()
lpi2c_runtime_suspend() pm_runtime_resume_and_get()
... lpi2c_imx_xfer()
...
rpm_suspend() set RPM_SUSPENDING pcf857x_set();
^^^^ B ...
clk_prepare_lock() --> hold prepare_lock
^^^^ A
...
Task 117 set power.runtime_status to RPM_SUSPENDING (A) and wait for task 120 release clock's global prepare mutex (B).
Task 120 hold global prepare mutex (B) and wait for power.runtime_status finish suspend (A).
The root cause is that the scope of global prepare_lock is too big. gpio-gate-clock and lpi2c clock are totally independent.
Although it may not happen at downstream case because [1], there are still have other i2c bus and spi bus, and other bus drivers. clock unprepare is quite common in runtime suspend functions.
[1] upstream driver have not use clk_unprepare in suspend functions.
The full log as below:
INFO: task kworker/2:3:117(T117) is blocked on a mutex likely owned by task kworker/u16:5:120(T120).
[ 6.955479][ T73] imx-lpi2c 42530000.i2c: lpi2c_runtime_suspend2
[ 6.957437][ T120] imx6q-pcie 4c300000.pcie: config reg[1] 0x60100000 == cpu 0x60100000
[ 6.957437][ T120] ; no fixup was ever needed for this devicetree
[ 6.964257][ T118] platform regulatory.0: Falling back to sysfs fallback for: regulatory.db
[ 6.973579][ T120] imx-lpi2c 42530000.i2c: lpi2c_runtime_resume1
[ 7.027143][ T120] imx-lpi2c 42530000.i2c: lpi2c_runtime_resume2 0
[ 7.033984][ T120] -----------pcf857x_set in
[ 7.038373][ T120] -----------------pcf857x_output in
[ 7.043527][ T120] ----------------- gpio->write in
[ 7.048520][ T117] imx-lpi2c 42530000.i2c: lpi2c_runtime_suspend
[ 7.054774][ T120] i2c i2c-2: msg[0] w0/r1 0, data[0] is 7f
[ 7.060448][ T120] i2c i2c-2: 42530000.i2c: pm_runtime_resume_and_get
[ 67.030316][ T118] cfg80211: failed to load regulatory.db
[ 244.059129][ T40] INFO: task kworker/2:3:117 blocked for more than 121 seconds.
[ 244.066619][ T40] Not tainted 6.15.0-rc2-next-20250417-06621-g7cd761409c73-dirty #7
[ 244.075010][ T40] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 244.083572][ T40] task:kworker/2:3 state:D stack:0 pid:117 tgid:117 ppid:2 task_flags:0x4208060 flags:0x00000008
[ 244.095438][ T40] Workqueue: pm pm_runtime_work
[ 244.100157][ T40] Call trace:
[ 244.103302][ T40] __switch_to+0xf8/0x1a0 (T)
[ 244.107882][ T40] __schedule+0x418/0xfd8
[ 244.112080][ T40] schedule+0x4c/0x164
[ 244.116055][ T40] schedule_preempt_disabled+0x24/0x40
[ 244.121392][ T40] __mutex_lock+0x1d4/0x580
[ 244.125798][ T40] mutex_lock_nested+0x24/0x30
[ 244.130436][ T40] clk_prepare_lock+0x4c/0xa8
[ 244.135018][ T40] clk_unprepare+0x24/0x44
[ 244.139298][ T40] clk_bulk_unprepare+0x38/0x60
[ 244.144048][ T40] lpi2c_runtime_suspend+0x64/0x9c
[ 244.149021][ T40] pm_generic_runtime_suspend+0x2c/0x44
[ 244.154475][ T40] __rpm_callback+0x48/0x1ec
[ 244.158935][ T40] rpm_callback+0x74/0x80
[ 244.163167][ T40] rpm_suspend+0x104/0x668
[ 244.167446][ T40] pm_runtime_work+0xc8/0xcc
[ 244.171939][ T40] process_one_work+0x214/0x62c
[ 244.176650][ T40] worker_thread+0x1ac/0x34c
[ 244.181144][ T40] kthread+0x144/0x220
[ 244.185082][ T40] ret_from_fork+0x10/0x20
[ 244.189435][ T40] INFO: task kworker/2:3:117 is blocked on a mutex likely owned by task kworker/u16:5:120.
[ 244.199300][ T40] task:kworker/u16:5 state:D stack:0 pid:120 tgid:120 ppid:2 task_flags:0x4208060 flags:0x00000008
[ 244.211164][ T40] Workqueue: async async_run_entry_fn
[ 244.216404][ T40] Call trace:
[ 244.219587][ T40] __switch_to+0xf8/0x1a0 (T)
[ 244.224127][ T40] __schedule+0x418/0xfd8
[ 244.228358][ T40] schedule+0x4c/0x164
[ 244.232298][ T40] rpm_resume+0x1c8/0x734
[ 244.236531][ T40] __pm_runtime_resume+0x50/0x98
[ 244.241338][ T40] lpi2c_imx_xfer+0x58/0xe60
[ 244.245829][ T40] __i2c_transfer+0x1c4/0x828
[ 244.250377][ T40] i2c_smbus_xfer_emulated+0x1b8/0x708
[ 244.255735][ T40] __i2c_smbus_xfer+0x1a0/0x6f0
[ 244.260447][ T40] i2c_smbus_xfer+0x98/0x120
[ 244.264939][ T40] i2c_smbus_write_byte+0x2c/0x3c
[ 244.269825][ T40] i2c_write_le8+0x10/0x20
[ 244.274152][ T40] pcf857x_output+0x7c/0xc0
[ 244.278527][ T40] pcf857x_set+0x3c/0x5c
[ 244.282672][ T40] gpiochip_set+0x68/0xc0
[ 244.286864][ T40] gpiod_set_raw_value_commit+0xd4/0x1a0
[ 244.292404][ T40] gpiod_set_value_nocheck+0x34/0x60
[ 244.297549][ T40] gpiod_set_value_cansleep+0x24/0x60
[ 244.302821][ T40] clk_sleeping_gpio_gate_prepare+0x18/0x28
[ 244.308582][ T40] clk_core_prepare+0xbc/0x2a8
[ 244.313247][ T40] clk_prepare+0x28/0x44
[ 244.317361][ T40] clk_bulk_prepare+0x34/0xa0
[ 244.321940][ T40] imx_pcie_host_init+0xe0/0x434
[ 244.326747][ T40] dw_pcie_host_init+0x1b8/0x758
[ 244.331587][ T40] imx_pcie_probe+0x380/0x8e0
[ 244.336133][ T40] platform_probe+0x68/0xd8
[ 244.340539][ T40] really_probe+0xbc/0x2bc
[ 244.344817][ T40] __driver_probe_device+0x78/0x120
[ 244.349916][ T40] driver_probe_device+0x3c/0x160
[ 244.354801][ T40] __device_attach_driver+0xb8/0x140
[ 244.359986][ T40] bus_for_each_drv+0x88/0xe8
[ 244.364534][ T40] __device_attach_async_helper+0xb8/0xdc
[ 244.370161][ T40] async_run_entry_fn+0x34/0xe0
[ 244.374882][ T40] process_one_work+0x214/0x62c
[ 244.379634][ T40] worker_thread+0x1ac/0x34c
[ 244.384102][ T40] kthread+0x144/0x220
[ 244.388076][ T40] ret_from_fork+0x10/0x20
Best Regard
Carlos Song
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