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During UFS initialization, devfreq initialization is asynchronous: ufshcd_async_scan() calls ufshcd_add_lus(), which in turn initializes devfreq for UFS. The simple ondemand governor is then loaded. If it is built as a module, request_module() is called and throws a warning: WARNING: CPU: 7 PID: 167 at kernel/kmod.c:136 __request_module+0x1e0/0x460 Modules linked in: crct10dif_ce llcc_qcom phy_qcom_qmp_usb ufs_qcom phy_qcom_snps_femto_v2 ufshcd_pltfrm phy_qcom_qmp_combo ufshcd_core phy_qcom_qmp_ufs qcom_wdt socinfo fuse ipv6 CPU: 7 PID: 167 Comm: kworker/u16:3 Not tainted 6.2.0-rc6-00009-g58706f7fb045 #1 Hardware name: Qualcomm SA8540P Ride (DT) Workqueue: events_unbound async_run_entry_fn pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : __request_module+0x1e0/0x460 lr : __request_module+0x1d8/0x460 sp : ffff800009323b90 x29: ffff800009323b90 x28: 0000000000000000 x27: 0000000000000000 x26: ffff800009323d50 x25: ffff7b9045f57810 x24: ffff7b9045f57830 x23: ffffdc5a83e426e8 x22: ffffdc5ae80a9818 x21: 0000000000000001 x20: ffffdc5ae7502f98 x19: ffff7b9045f57800 x18: ffffffffffffffff x17: 312f716572667665 x16: 642f7366752e3030 x15: 0000000000000000 x14: 000000000000021c x13: 0000000000005400 x12: ffff7b9042ed7614 x11: ffff7b9042ed7600 x10: 00000000636c0890 x9 : 0000000000000038 x8 : ffff7b9045f2c880 x7 : ffff7b9045f57c68 x6 : 0000000000000080 x5 : 0000000000000000 x4 : 8000000000000000 x3 : 0000000000000000 x2 : 0000000000000000 x1 : ffffdc5ae5d382f0 x0 : 0000000000000001 Call trace: __request_module+0x1e0/0x460 try_then_request_governor+0x7c/0x100 devfreq_add_device+0x4b0/0x5fc ufshcd_async_scan+0x1d4/0x310 [ufshcd_core] async_run_entry_fn+0x34/0xe0 process_one_work+0x1d0/0x320 worker_thread+0x14c/0x444 kthread+0x10c/0x110 ret_from_fork+0x10/0x20 This occurs because synchronous module loading from async is not allowed. According to __request_module(): /* * We don't allow synchronous module loading from async. Module * init may invoke async_synchronize_full() which will end up * waiting for this task which already is waiting for the module * loading to complete, leading to a deadlock. */ Such a deadlock was experienced on the Qualcomm QDrive3/sa8540p-ride. With DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning. Fix both the warning and the deadlock by moving devfreq initialization out of the async routine. Tested on the sa8540p-ride by using fio to put the UFS under load, and printing the trace generated by /sys/kernel/tracing/events/ufs/ufshcd_clk_scaling events. The trace looks similar with and without the change. Link: https://lore.kernel.org/r/20230217194423.42553-1-athierry@redhat.com Signed-off-by: Adrien Thierry <athierry@redhat.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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| .. | ||
| ufs_quirks.h | ||
| ufs.h | ||
| ufshcd.h | ||
| ufshci.h | ||
| unipro.h | ||