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
