Hey John,
In my testing I've come across another issue in the dwc2 driver.
Basically when plugging in various cables in different orders, I'm
occasionally seeing the following BUG splat:
[ 86.215403] BUG: scheduling while atomic: kworker/u16:2/53/0x00000002
[ 86.219164] usb 1-1: USB disconnect, device number 9
[ 86.226845] Preemption disabled at:[ 86.230218]
[<ffffff8008673558>] dwc2_conn_id_status_change+0x120/0x250
[ 86.236894] CPU: 0 PID: 53 Comm: kworker/u16:2 Tainted: G W
4.9.0-rc8-00051-gd5a7979-dirty #1702
[ 86.246836] Hardware name: HiKey Development Board (DT)
[ 86.252100] Workqueue: dwc2 dwc2_conn_id_status_change
[ 86.257279] Call trace:
[ 86.259771] [<ffffff8008087c28>] dump_backtrace+0x0/0x1a0
[ 86.265210] [<ffffff8008087ddc>] show_stack+0x14/0x20
[ 86.270308] [<ffffff80084343f0>] dump_stack+0x90/0xb0
[ 86.275401] [<ffffff80080d8d94>] __schedule_bug+0x6c/0xb8
[ 86.280841] [<ffffff8008a07220>] __schedule+0x4f8/0x5b0
[ 86.286099] [<ffffff8008a073e8>] schedule+0x38/0xa0
[ 86.291017] [<ffffff8008a0a6cc>] schedule_hrtimeout_range_clock+0x8c/0xf0
[ 86.297846] [<ffffff8008a0a740>] schedule_hrtimeout_range+0x10/0x18
[ 86.304150] [<ffffff8008a0a4a0>] usleep_range+0x50/0x58
[ 86.309418] [<ffffff800866d8dc>] dwc2_wait_for_mode.isra.4+0x54/0xd0
[ 86.315815] [<ffffff800866f058>] dwc2_core_reset+0xe0/0x168
[ 86.321431] [<ffffff800867e364>] dwc2_hsotg_core_init_disconnected+0x2c/0x310
[ 86.328602] [<ffffff8008673568>] dwc2_conn_id_status_change+0x130/0x250
[ 86.335254] [<ffffff80080ccd48>] process_one_work+0x118/0x370
[ 86.341035] [<ffffff80080ccfe8>] worker_thread+0x48/0x498
[ 86.346473] [<ffffff80080d2eb0>] kthread+0xd0/0xe8
[ 86.351299] [<ffffff8008082e80>] ret_from_fork+0x10/0x50
This seems to be caused by the dwc2_wait_for_mode() calling
usleep_range() while the hstog->lock spinlock is held, since we take
that before calling dwc2_hsotg_core_init_disconnected().
I'm sort of surprised this hasn't been noticed before, since it seems
dwc2_hsotg_core_init_disconnected() is called from a number of places
with the spinlock held.
I'm really not sure about the locking rules for this driver, but does
dropping the lock while we do the sleep, then requiring it, an ok
solution here?
thanks
-john
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