Kernel WARNING (RCU) with btnxpuart on TI AM62 platform
Francesco Dolcini
francesco at dolcini.it
Wed Apr 9 23:20:06 PDT 2025
Hello Vignesh,
On Tue, Apr 08, 2025 at 09:15:26PM +0530, Vignesh Raghavendra wrote:
> On 08/04/25 14:05, Francesco Dolcini wrote:
> > I do have the following kernel warning with 6.15-rc1, on a TI AM62
> > platform (arm64), single CPU core, using btnxpuart driver, any idea?
> > PREEMPT_RT is enabled, if it matters.
> >
> > Either the issue is not systematic, or multi cores SoCs are not affected
> > (no error on the exact same image on a dual nor on quad core TI AM62).
> >
> >
> > [ 23.139080] Voluntary context switch within RCU read-side critical section!
> > [ 23.139119] WARNING: CPU: 0 PID: 61 at /kernel/rcu/tree_plugin.h:332 rcu_note_context_switch+0x3c4/0x430
> > [ 23.139172] Modules linked in: uas onboard_usb_dev optee_rng dwc3 evdev btnxpuart spidev aes_ce_blk aes_ce_cipher ghash_ce gf128mul sha2_ce sha256_arm64 sha1_ce snd_soc_simple_card snd_soc_simple_card_utils optee spi_cadence_quadspi tee gpio_keys usb_conn_gpio display_connector roles dwc3_am62 mwifiex_sdio k3_j72xx_bandgap mwifiex rtc_ti_k3 cfg80211 tidss sa2ul sha512_generic snd_soc_davinci_mcasp authenc drm_display_helper snd_soc_ti_udma crypto_null snd_soc_ti_edma sha1_generic snd_soc_ti_sdma omap_hwspinlock lontium_lt8912b ina2xx snd_soc_wm8904 ti_ads1015 industrialio_triggered_buffer kfifo_buf lm75 tpm_tis_i2c tps65219_pwrbutton crc_ccitt tpm_tis_core tpm rng_core tc358768 m_can_platform pwm_tiehrpwm m_can spi_omap2_mcspi can_dev bluetooth ecdh_generic ecc rfkill libaes loop fuse ipv6 autofs4
> > [ 23.139459] CPU: 0 UID: 0 PID: 61 Comm: kworker/u5:0 Not tainted 6.15.0-rc1-0.0.0-devel #1 PREEMPT_RT
> > [ 23.139471] Hardware name: Toradex Verdin AM62 WB on Dahlia Board (DT)
> > [ 23.139478] Workqueue: hci0 hci_power_off [bluetooth]
> > [ 23.139615] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [ 23.139625] pc : rcu_note_context_switch+0x3c4/0x430
> > [ 23.139647] lr : rcu_note_context_switch+0x3c4/0x430
> > [ 23.139658] sp : ffff8000819fb740
> > [ 23.139661] x29: ffff8000819fb740 x28: 0000000000000000 x27: ffff0000079d2010
> > [ 23.139673] x26: ffff0000011e7810 x25: ffff000001c2c200 x24: 0000000000000000
> > [ 23.139688] x23: 0000000000000000 x22: ffff000001c2c200 x21: ffff000001c2c200
> > [ 23.139700] x20: ffff800081083ec0 x19: ffff00001da9fec0 x18: fffffffffffe7e78
> > [ 23.139712] x17: ffff7fff9ca1c000 x16: ffff800080000000 x15: ffff00001da9f8c0
> > [ 23.139726] x14: fffffffffffc7e77 x13: 216e6f6974636573 x12: 206c616369746972
> > [ 23.139738] x11: 6320656469732d64 x10: 6165722055435220 x9 : 206e696874697720
> > [ 23.139750] x8 : ffff80008113f040 x7 : ffff8000819fb4e0 x6 : 000000000000000c
> > [ 23.139761] x5 : ffff00001da95888 x4 : 0000000000000000 x3 : 0000000000000027
> > [ 23.139775] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000001c2c200
> > [ 23.139788] Call trace:
> > [ 23.139793] rcu_note_context_switch+0x3c4/0x430 (P)
> > [ 23.139813] __schedule+0xa0/0x7dc
> > [ 23.139830] schedule+0x34/0x11c
> > [ 23.139841] schedule_timeout+0x8c/0x110
> > [ 23.139861] wait_for_completion_timeout+0x78/0x14c
> > [ 23.139873] ti_sci_set_device_state+0x120/0x1fc
> > [ 23.139886] ti_sci_cmd_get_device_exclusive+0x18/0x30
> > [ 23.139899] ti_sci_pd_power_on+0x28/0x54
> > [ 23.139916] _genpd_power_on+0x98/0x188
> > [ 23.139927] genpd_power_on+0xa8/0x168
> > [ 23.139940] genpd_runtime_resume+0xc0/0x298
> > [ 23.139957] __rpm_callback+0x48/0x1a4
> > [ 23.139974] rpm_callback+0x74/0x80
> > [ 23.139987] rpm_resume+0x3b0/0x698
> > [ 23.140000] __pm_runtime_resume+0x48/0x88
> > [ 23.140012] omap8250_set_mctrl+0x2c/0xbc
> > [ 23.140030] serial8250_set_mctrl+0x20/0x40
> > [ 23.140046] uart_update_mctrl+0x80/0x110
>
> I think issue is that uart_update_mctrl() holds a spinlock:
>
> uart_port_lock_irqsave(port, &flags);
>
> and then omap8250_set_mctrl() calls pm_runtime APIs which on K3 SoC
> needs to talk to a Firmware to enable pd. This IPC call is a sleeping
> call leading to scheduling with IRQs disabled.
>
> I guess this is what RT linux is complaining? I dont have a solution
> though, maybe serdev delays pm_runtime_put till the port is closed?
Our CI reproduced what looks like the same issue also on current
torvalds/master (6.15-rc1+) branch, without PREEMPT_RT.
The call trace seems just the same, but attaching it here for
completeness.
[ 20.931923] BUG: scheduling while atomic: kworker/u5:0/42/0x00000002
[ 20.938429] Modules linked in: sd_mod uas onboard_usb_dev btnxpuart optee_rng dwc3 evdev spidev aes_ce_blk aes_ce_cipher ghash_ce gf128mul sha2_ce sha256_arm64 sha1_ce snd_soc_simple_card snd_soc_simple_card_utils mwifiex_sdio mwifiex display_connector spi_cadence_quadspi optee usb_conn_gpio tee gpio_keys roles k3_j72xx_bandgap cfg80211 rtc_ti_k3 dwc3_am62 bluetooth ecdh_generic ecc sa2ul sha512_generic rfkill authenc tidss crypto_null libaes snd_soc_davinci_mcasp sha1_generic drm_display_helper snd_soc_ti_udma snd_soc_ti_edma snd_soc_ti_sdma omap_hwspinlock lontium_lt8912b ina2xx ti_ads1015 snd_soc_wm8904 industrialio_triggered_buffer kfifo_buf lm75 tpm_tis_i2c crc_ccitt tps65219_pwrbutton tpm_tis_core tpm m_can_platform m_can rng_core tc358768 can_dev pwm_tiehrpwm spi_omap2_mcspi loop fuse ipv6 autofs4
[ 20.938865] CPU: 0 UID: 0 PID: 42 Comm: kworker/u5:0 Not tainted 6.15.0-rc1-0.0.0-devel #1 PREEMPT
[ 20.938878] Hardware name: Toradex Verdin AM62 WB on Dahlia Board (DT)
[ 20.938895] Workqueue: hci0 hci_power_off [bluetooth]
[ 20.939032] Call trace:
[ 20.939037] show_stack+0x2c/0x84 (C)
[ 20.939063] dump_stack_lvl+0x60/0x80
[ 20.939084] dump_stack+0x18/0x24
[ 20.939096] __schedule_bug+0x54/0x70
[ 20.939116] __schedule+0x628/0x7dc
[ 20.939129] schedule+0x34/0x11c
[ 20.939138] rpm_resume+0x17c/0x6a0
[ 20.939155] __pm_runtime_resume+0x50/0x9c
[ 20.939168] omap8250_set_mctrl+0x2c/0xc0
[ 20.939183] serial8250_set_mctrl+0x20/0x40
[ 20.939193] uart_update_mctrl+0x88/0x11c
[ 20.939215] uart_dtr_rts+0x104/0x120
[ 20.939226] tty_port_shutdown+0xd4/0xdc
[ 20.939236] tty_port_close+0x40/0xc0
[ 20.939248] uart_close+0x34/0x9c
[ 20.939259] ttyport_close+0x50/0xa0
[ 20.939272] serdev_device_close+0x40/0x5c
[ 20.939283] btnxpuart_close+0x1c/0xa0 [btnxpuart]
[ 20.939309] hci_dev_close_sync+0x304/0x7cc [bluetooth]
[ 20.939376] hci_dev_do_close+0x2c/0x70 [bluetooth]
[ 20.939441] hci_power_off+0x20/0x64 [bluetooth]
[ 20.939508] process_one_work+0x148/0x290
[ 20.939528] worker_thread+0x2c8/0x3e4
[ 20.939541] kthread+0x12c/0x204
[ 20.939554] ret_from_fork+0x10/0x20
[ 20.943567] BUG: scheduling while atomic: kworker/u5:0/42/0x00000000
[ 20.950126] Modules linked in: sd_mod uas onboard_usb_dev btnxpuart optee_rng dwc3 evdev spidev aes_ce_blk aes_ce_cipher ghash_ce gf128mul sha2_ce sha256_arm64 sha1_ce snd_soc_simple_card snd_soc_simple_card_utils mwifiex_sdio mwifiex display_connector spi_cadence_quadspi optee usb_conn_gpio tee gpio_keys roles k3_j72xx_bandgap cfg80211 rtc_ti_k3 dwc3_am62 bluetooth ecdh_generic ecc sa2ul sha512_generic rfkill authenc tidss crypto_null libaes snd_soc_davinci_mcasp sha1_generic drm_display_helper snd_soc_ti_udma snd_soc_ti_edma snd_soc_ti_sdma omap_hwspinlock lontium_lt8912b ina2xx ti_ads1015 snd_soc_wm8904 industrialio_triggered_buffer kfifo_buf lm75 tpm_tis_i2c crc_ccitt tps65219_pwrbutton tpm_tis_core tpm m_can_platform m_can rng_core tc358768 can_dev pwm_tiehrpwm spi_omap2_mcspi loop fuse ipv6 autofs4
[ 20.950550] CPU: 0 UID: 0 PID: 42 Comm: kworker/u5:0 Tainted: G W 6.15.0-rc1-0.0.0-devel #1 PREEMPT
[ 20.950566] Tainted: [W]=WARN
[ 20.950570] Hardware name: Toradex Verdin AM62 WB on Dahlia Board (DT)
[ 20.950584] Workqueue: hci0 hci_power_off [bluetooth]
[ 20.950721] Call trace:
[ 20.950726] show_stack+0x2c/0x84 (C)
[ 20.950747] dump_stack_lvl+0x60/0x80
[ 20.950771] dump_stack+0x18/0x24
[ 20.950783] __schedule_bug+0x54/0x70
[ 20.950798] __schedule+0x628/0x7dc
[ 20.950815] schedule+0x34/0x11c
[ 20.950824] schedule_timeout+0xd4/0x110
[ 20.950838] wait_for_completion+0x78/0x140
[ 20.950853] __flush_work+0x250/0x340
[ 20.950868] flush_work+0x14/0x20
[ 20.950879] omap_8250_shutdown+0x2c/0x1a4
[ 20.950903] serial8250_shutdown+0x18/0x40
[ 20.950913] uart_port_shutdown+0x40/0x58
[ 20.950926] uart_tty_port_shutdown+0x5c/0x178
[ 20.950940] tty_port_shutdown+0x84/0xdc
[ 20.950950] tty_port_close+0x40/0xc0
[ 20.950958] uart_close+0x34/0x9c
[ 20.950969] ttyport_close+0x50/0xa0
[ 20.950990] serdev_device_close+0x40/0x5c
[ 20.951001] btnxpuart_close+0x1c/0xa0 [btnxpuart]
[ 20.951017] hci_dev_close_sync+0x304/0x7cc [bluetooth]
[ 20.951082] hci_dev_do_close+0x2c/0x70 [bluetooth]
[ 20.951149] hci_power_off+0x20/0x64 [bluetooth]
[ 20.951214] process_one_work+0x148/0x290
[ 20.951227] worker_thread+0x2c8/0x3e4
[ 20.951242] kthread+0x12c/0x204
[ 20.951258] ret_from_fork+0x10/0x20
Francesco
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