Re: USB gadget regression on v6.4-rc1 and v6.1.28

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On Mon, May 15, 2023 at 01:38:30PM -0700, Badhri Jagan Sridharan wrote:
> Do you see the system to crash (or) wait indefinitely for the gadget
> being pulled up ?
It wait indefinitely. Likely a deadlock.

> Is it possible to get the stack trace ?
I was able to generate this enabling some debugging kconfig:

[   41.341580] ============================================
[   41.349246] WARNING: possible recursive locking detected
[   41.357120] 6.4.0-rc1-0.0.0-devel-00005-gcda3c69ebc14 #1 Not tainted
[   41.357138] --------------------------------------------
[   41.357143] echo/566 is trying to acquire lock:
[   41.357153] c4b0a72c (&udc->connect_lock){+.+.}-{4:4}, at: usb_udc_vbus_handler+0x1c/0x60
[   41.357209]
[   41.357209] but task is already holding lock:
[   41.357214] c4b0a72c (&udc->connect_lock){+.+.}-{4:4}, at: gadget_bind_driver+0x110/0x230
[   41.357263]
[   41.357263] other info that might help us debug this:
[   41.357272]  Possible unsafe locking scenario:
[   41.357272]
[   41.357279]        CPU0
[   41.357285]        ----
[   41.357291]   lock(&udc->connect_lock);
[   41.357304]   lock(&udc->connect_lock);
[   41.357316]
[   41.357316]  *** DEADLOCK ***
[   41.357316]
[   41.357319]  May be due to missing lock nesting notation
[   41.357319]
[   41.357324] 6 locks held by echo/566:
[   41.357332]  #0: c430fabc (sb_writers#11){.+.+}-{0:0}, at: ksys_write+0x70/0xf8
[   41.357377]  #1: c5b26e98 (&buffer->mutex){+.+.}-{4:4}, at: configfs_write_iter+0x24/0x118
[   41.357420]  #2: c5284548 (&p->frag_sem){.+.+}-{4:4}, at: configfs_write_iter+0x88/0x118
[   41.357462]  #3: c55a2a20 (&gi->lock){+.+.}-{4:4}, at: gadget_dev_desc_UDC_store+0x58/0x110
[   41.357503]  #4: c4b5648c (&dev->mutex){....}-{4:4}, at: __driver_attach+0x108/0x1cc
[   41.357538]  #5: c4b0a72c (&udc->connect_lock){+.+.}-{4:4}, at: gadget_bind_driver+0x110/0x230
[   41.357578]
[   41.357578] stack backtrace:
[   41.357585] CPU: 1 PID: 566 Comm: echo Not tainted 6.4.0-rc1-0.0.0-devel-00005-gcda3c69ebc14 #1
[   41.357596] Hardware name: Freescale i.MX7 Dual (Device Tree)
[   41.357612]  unwind_backtrace from show_stack+0x10/0x14
[   41.357639]  show_stack from dump_stack_lvl+0x70/0xb0
[   41.357660]  dump_stack_lvl from __lock_acquire+0x924/0x22c4
[   41.357681]  __lock_acquire from lock_acquire+0x100/0x370
[   41.357699]  lock_acquire from __mutex_lock+0xa8/0xfb4
[   41.357720]  __mutex_lock from mutex_lock_nested+0x1c/0x24
[   41.357742]  mutex_lock_nested from usb_udc_vbus_handler+0x1c/0x60
[   41.357769]  usb_udc_vbus_handler from ci_udc_start+0x74/0x9c
[   41.357798]  ci_udc_start from gadget_bind_driver+0x130/0x230
[   41.357824]  gadget_bind_driver from really_probe+0xd8/0x3fc
[   41.357846]  really_probe from __driver_probe_device+0x94/0x1f0
[   41.357862]  __driver_probe_device from driver_probe_device+0x2c/0xc4
[   41.357877]  driver_probe_device from __driver_attach+0x114/0x1cc
[   41.357893]  __driver_attach from bus_for_each_dev+0x7c/0xcc
[   41.357915]  bus_for_each_dev from bus_add_driver+0xd4/0x200
[   41.357942]  bus_add_driver from driver_register+0x7c/0x114
[   41.357965]  driver_register from usb_gadget_register_driver_owner+0x40/0xe0
[   41.357987]  usb_gadget_register_driver_owner from gadget_dev_desc_UDC_store+0xd4/0x110
[   41.358014]  gadget_dev_desc_UDC_store from configfs_write_iter+0xac/0x118
[   41.358042]  configfs_write_iter from vfs_write+0x1b4/0x40c
[   41.358068]  vfs_write from ksys_write+0x70/0xf8
[   41.358088]  ksys_write from ret_fast_syscall+0x0/0x1c
[   41.358106] Exception stack(0xf0f15fa8 to 0xf0f15ff0)
[   41.358119] 5fa0:                   0000000a 00a741c0 00000001 00a741c0 0000000a 00000001
[   41.358132] 5fc0: 0000000a 00a741c0 b6f7dba0 00000004 0000000a 00000001 00000000 b6f7d388
[   41.358141] 5fe0: 00000004 beec4b80 b6f1c1f3 b6e9b5f6



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