On Sat, Sep 05, 2020 at 06:42:49PM +0200, Uwe Kleine-König wrote: > On Wed, Sep 02, 2020 at 02:12:34PM +0200, Vincent Whitchurch wrote: > > v2: > > - [..] > > - Stop PWM before unregister > > I didn't take the time yet to look at v2, but just spotted this which is > wrong. .remove() is not supposed to modify the output. (If the PWM is > still running in .remove() this is either because it was running at > bootup and was never modified or is a bug in the consumer code.) If the PWM is not stopped while unregistering, the hrtimer will still be active and unloading the module will result in a crash when the next callback hits. The consumer can be userspace via sysfs. # insmod /pwm-gpio.ko # lsmod Module Size Used by Not tainted pwm_gpio 16384 0 # cd /sys/class/pwm/ # ls pwmchip0 # cd pwmchip0/ # ls device export npwm power subsystem uevent unexport # echo 0 > export # ls device npwm pwm0 uevent export power subsystem unexport # cd pwm0/ # ls capture enable polarity uevent duty_cycle period power # echo 100000 > period # echo 10000 > duty_cycle # echo 1 > enable # lsmod Module Size Used by Not tainted pwm_gpio 16384 1 # echo 0 > unexport # lsmod Module Size Used by Not tainted pwm_gpio 16384 0 # rmmod pwm_gpio # [ 79.609675][ C0] 8<--- cut here --- [ 79.610551][ C0] Unable to handle kernel paging request at virtual address 7f0000ac [ 79.611933][ C0] pgd = (ptrval) [ 79.612588][ C0] [7f0000ac] *pgd=683df811, *pte=00000000, *ppte=00000000 [ 79.615083][ C0] Internal error: Oops: 80000007 [#1] SMP ARM [ 79.616194][ C0] Modules linked in: [last unloaded: pwm_gpio] [ 79.617605][ C0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.8.0+ #118 [ 79.618535][ C0] Hardware name: ARM-Versatile Express [ 79.620086][ C0] PC is at 0x7f0000ac [ 79.621402][ C0] LR is at __hrtimer_run_queues+0x104/0x5ec [ 79.622143][ C0] pc : [<7f0000ac>] lr : [<801b75a8>] psr: 600e0193 [ 79.622908][ C0] sp : 80d01da0 ip : 88069868 fp : 7f0000ac [ 79.623612][ C0] r10: 80d88c1d r9 : 80d00000 r8 : be79e000 [ 79.624271][ C0] r7 : be79e000 r6 : 80d08cac r5 : be79e058 r4 : 88069868 [ 79.625044][ C0] r3 : 00000000 r2 : 80d0bb80 r1 : 00000001 r0 : 88069868 [ 79.625954][ C0] Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none [ 79.626319][ C0] Control: 10c5387d Table: 68344059 DAC: 00000051 [ 79.626470][ C0] Process swapper/0 (pid: 0, stack limit = 0x(ptrval)) [ 79.626632][ C0] Stack: (0x80d01da0 to 0x80d02000) [ 79.626884][ C0] 1da0: 80d89ff8 80d89fe4 80d89fd0 00000000 80d092ec 00000000 882c2208 00000012 [ 79.627175][ C0] 1dc0: 80adab04 80d08c88 882c2208 00000012 be79e110 12f46c55 801b834c be79e000 [ 79.627443][ C0] 1de0: 800e0193 882c2208 00000012 be79e150 be79e110 80d89a80 80d01f68 801b83dc [ 79.627712][ C0] 1e00: 800e0193 0000000f 80d89d78 80c4f780 3db4e000 80d05d40 801c863c be02da00 [ 79.627974][ C0] 1e20: 00000000 801b65b4 00000000 ffffe000 80d05d40 801b6608 00989680 00000000 [ 79.628235][ C0] 1e40: 80d05d40 801c8360 00000001 00000000 801c863c 801543bc 00000000 ffffffff [ 79.628563][ C0] 1e60: 7fffffff be7a7800 00000011 801c863c 80d08c88 be031480 80d89a94 00000001 [ 79.628843][ C0] 1e80: be031480 80d89a94 00000011 be02da00 80d08cac 80110e58 80d88bf4 80196ebc [ 79.629117][ C0] 1ea0: 00000001 80d09314 88129720 80c54f38 00000000 00000000 00000001 be018400 [ 79.629393][ C0] 1ec0: c0803100 00000000 80d01f68 8019068c 80c54f38 80190cbc 80d4f7d4 80d09314 [ 79.629661][ C0] 1ee0: c080210c 80d01f10 c0802100 80523270 801090e8 600e0013 ffffffff 80d01f44 [ 79.629923][ C0] 1f00: 00000001 80d00000 00000000 80100af0 ffffffff 00000001 3db4e000 00012ef9 [ 79.630184][ C0] 1f20: 00000000 80d00000 80d08cac 80d08ce8 00000001 80c553d0 00000000 80d01f68 [ 79.630456][ C0] 1f40: 3db4e000 80d01f60 801090e4 801090e8 600e0013 ffffffff 00000051 00000000 [ 79.630723][ C0] 1f60: 00000000 8015e28c 80d01f7c 808b85b4 80d08c88 80d89410 80d01f8c 12f46c55 [ 79.630985][ C0] 1f80: 80d88b34 000000d6 80d08c88 80d08c80 80d9d040 80c3ba58 00000027 80c3ba58 [ 79.631257][ C0] 1fa0: befffe00 8015e754 00000001 80c00e6c ffffffff ffffffff 00000000 80c0059c [ 79.631525][ C0] 1fc0: 00000000 80c3ba58 12f16455 00000000 00000000 80c00330 00000051 10c0387d [ 79.631790][ C0] 1fe0: 000008e0 687c9000 410fc090 10c5387d 00000000 00000000 00000000 00000000 [ 79.632114][ C0] [<801b75a8>] (__hrtimer_run_queues) from [<801b83dc>] (hrtimer_run_queues+0xb8/0xcc) [ 79.632342][ C0] [<801b83dc>] (hrtimer_run_queues) from [<801b65b4>] (run_local_timers+0x14/0x40) [ 79.632540][ C0] [<801b65b4>] (run_local_timers) from [<801b6608>] (update_process_times+0x28/0x88) [ 79.632739][ C0] [<801b6608>] (update_process_times) from [<801c8360>] (tick_periodic+0x40/0x184) [ 79.632938][ C0] [<801c8360>] (tick_periodic) from [<801c863c>] (tick_handle_periodic+0x28/0x88) [ 79.633140][ C0] [<801c863c>] (tick_handle_periodic) from [<80110e58>] (twd_handler+0x30/0x38) [ 79.633342][ C0] [<80110e58>] (twd_handler) from [<80196ebc>] (handle_percpu_devid_irq+0xd8/0x3ec) [ 79.633549][ C0] [<80196ebc>] (handle_percpu_devid_irq) from [<8019068c>] (generic_handle_irq+0x34/0x44) [ 79.633760][ C0] [<8019068c>] (generic_handle_irq) from [<80190cbc>] (__handle_domain_irq+0x5c/0xb4) [ 79.633965][ C0] [<80190cbc>] (__handle_domain_irq) from [<80523270>] (gic_handle_irq+0x4c/0x90) [ 79.634157][ C0] [<80523270>] (gic_handle_irq) from [<80100af0>] (__irq_svc+0x70/0x98) [ 79.634342][ C0] Exception stack(0x80d01f10 to 0x80d01f58) [ 79.634519][ C0] 1f00: ffffffff 00000001 3db4e000 00012ef9 [ 79.634781][ C0] 1f20: 00000000 80d00000 80d08cac 80d08ce8 00000001 80c553d0 00000000 80d01f68 [ 79.635016][ C0] 1f40: 3db4e000 80d01f60 801090e4 801090e8 600e0013 ffffffff [ 79.635190][ C0] [<80100af0>] (__irq_svc) from [<801090e8>] (arch_cpu_idle+0x24/0x3c) [ 79.635368][ C0] [<801090e8>] (arch_cpu_idle) from [<8015e28c>] (do_idle+0x190/0x26c) [ 79.635534][ C0] [<8015e28c>] (do_idle) from [<8015e754>] (cpu_startup_entry+0x18/0x1c) [ 79.635699][ C0] [<8015e754>] (cpu_startup_entry) from [<80c00e6c>] (start_kernel+0x504/0x53c) [ 79.635978][ C0] Code: bad PC value [ 79.636268][ C0] ---[ end trace 3c6c5034e210d496 ]--- [ 79.636496][ C0] Kernel panic - not syncing: Fatal exception in interrupt [ 79.636912][ C0] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
