Thanks for your suggestion, I should mention that I only see the spinlock on the midi transmit side, not when receiving. I have tried the proposed fixes and cherry-picked commits c7d9efdff68e and 8653d71ce376 (the equivalent fix in f_midi.c), and upgraded to v5.10rt. I still see the spin lock in both cases but the trace is slightly different: [ 193.010603] kernel BUG at /kernel-source//kernel/locking/rtmutex.c:1048! [ 193.010609] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [ 193.010644] Process kworker/4:2H (pid: 847, stack limit = 0x000000006e538c8b) [ 193.010666] Workqueue: events_highpri f_midi_in_work [usb_f_midi] [ 193.010671] pstate: 60000085 (nZCv daIf -PAN -UAO) [ 193.010686] pc : rt_spin_lock_slowlock_locked+0x280/0x2b8 [ 193.010690] lr : rt_spin_lock_slowlock_locked+0x34/0x2b8 [ 193.010691] sp : ffff00000c273a60 [ 193.010693] x29: ffff00000c273a60 x28: ffff80053573c000 [ 193.010696] x27: ffff80053573c220 x26: 0000000000000000 [ 193.010699] x25: ffff80053575bc00 x24: 0000000000000000 [ 193.010702] x23: ffff80053573c1d0 x22: ffff00000c273af8 [ 193.010705] x21: ffff800537ced400 x20: ffff00000c273af8 [ 193.010707] x19: ffff80053573c1e8 x18: 0000000000000000 [ 193.010709] x17: 0000000000000000 x16: 0000000000000000 [ 193.010711] x15: 0000000000000400 x14: 0000000000000400 [ 193.010713] x13: 0000000000000001 x12: 0000000000000000 [ 193.010715] x11: 00000000000001a4 x10: 0000000000000a10 [ 193.010718] x9 : ffff00000c273d60 x8 : 0000000000000000 [ 193.010720] x7 : ffff800537ced400 x6 : ffff800537ced401 [ 193.010722] x5 : ffff80053573c200 x4 : ffff800537ced401 [ 193.010724] x3 : 0000000000000001 x2 : 0000000000000000 [ 193.010726] x1 : ffff800537ced400 x0 : ffff800537ced400 [ 193.010729] Call trace: [ 193.010733] rt_spin_lock_slowlock_locked+0x280/0x2b8 [ 193.010736] rt_spin_lock_slowlock+0x5c/0x90 [ 193.010739] rt_spin_lock+0x60/0x70 [ 193.010742] f_midi_transmit+0x90/0x5d8 [usb_f_midi] [ 193.010745] f_midi_complete+0x11c/0x138 [usb_f_midi] [ 193.010754] usb_gadget_giveback_request+0x10/0x18 [ 193.010758] __usbhsg_queue_pop+0x3c/0x58 [ 193.010760] usbhsg_queue_done+0x44/0x60 [ 193.010763] usbhsf_pkt_handler+0x80/0x120 [ 193.010766] usbhs_pkt_start+0x10/0x18 [ 193.010768] usbhsg_queue_push.isra.0+0x44/0x50 [ 193.010771] usbhsg_ep_queue+0x2c/0x40 [ 193.010773] usb_ep_queue+0x24/0x40 [ 193.010776] f_midi_transmit+0x238/0x5d8 [usb_f_midi] [ 193.010779] f_midi_in_work+0x10/0x18 [usb_f_midi] [ 193.010786] process_one_work+0x1e8/0x340 [ 193.010788] worker_thread+0x40/0x458 [ 193.010792] kthread+0x16c/0x170 [ 193.010797] ret_from_fork+0x10/0x1c [ 193.010801] Code: a90363b7 f9000fb4 f90023b9 f9002bbb (d4210000) [ 193.271972] ---[ end trace 0000000000000002 ]--- [ 193.271976] note: kworker/4:2H[847] exited with preempt_count 1 Let me know if there is anything more useful here or if there's any other information I can provide. Thanks On Thu, Jan 23, 2025 at 6:23 AM Petr Tesařík <petesarik@xxxxxxx> wrote: > > V Tue, 14 Jan 2025 23:05:10 -0500 > Jillian Donahue <jilliandonahue58@xxxxxxxxx> napsáno: > > > Hello, > > > > I am working on getting USB MIDI enabled for my device and keep > > running into this issue: > > > > [ 125.702601] kernel BUG at /kernel-source//kernel/locking/rtmutex.c:1048! > > [ 125.702607] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > > > > [ 125.702764] Call trace: > > [ 125.702770] rt_spin_lock_slowlock_locked+0x280/0x2b8 > > [ 125.702774] rt_spin_lock_slowlock+0x5c/0x90 > > [ 125.702779] rt_spin_lock+0x60/0x70 > > [ 125.702792] f_midi_transmit+0x90/0x5d8 [usb_f_midi] > > [ 125.702797] f_midi_complete+0x11c/0x138 [usb_f_midi] > > [ 125.702809] usb_gadget_giveback_request+0x10/0x18 > > [ 125.702814] __usbhsg_queue_pop+0x3c/0x58 > > [ 125.702818] usbhsg_queue_done+0x44/0x60 > > [ 125.702822] usbhsf_pkt_handler+0x80/0x120 > > [ 125.702826] usbhs_pkt_start+0x10/0x18 > > [ 125.702830] usbhsg_queue_push.isra.0+0x44/0x50 > > [ 125.702834] usbhsg_ep_queue+0x2c/0x40 > > [ 125.702837] usb_ep_queue+0x24/0x40 > > [ 125.702843] f_midi_transmit+0x238/0x5d8 [usb_f_midi] > > [ 125.702848] f_midi_in_tasklet+0xc/0x18 [usb_f_midi] > > [ 125.702860] tasklet_action_common.isra.2+0xcc/0x1f0 > > [ 125.702864] tasklet_hi_action+0x20/0x28 > > [ 125.702869] do_current_softirqs+0x19c/0x248 > > [ 125.702873] run_ksoftirqd+0x24/0x40 > > [ 125.702883] smpboot_thread_fn+0x1b0/0x2b8 > > [ 125.702887] kthread+0x16c/0x170 > > [ 125.702894] ret_from_fork+0x10/0x1c > > [ 125.702900] Code: a90363b7 f9000fb4 f90023b9 f9002bbb (d4210000) > > [ 125.966631] ---[ end trace 0000000000000002 ]--- > > > > Seen in the driver code here: > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/usb/gadget/function/f_midi.c?h=v4.19.182#n683 > > > > We are running a 4.19.182 kernel patched to PREEMPT RT. > > > > Has anyone come across this before? > > I also ask if we've uncovered a bug when using the midi usb gadget > > with PREEMPT RT. > > If so, do you have any suggestions for a proper fix? > > AFAICT the proper fix would be to replace tasklets with a work (as done > in commit c7d9efdff68e). IOW either upgrade to v5.10rt, or backport the > referenced commit. > > HTH > Petr T
