USB: gadget: f_hid: fix deadlock in f_hidg_write()
In f_hidg_write() the write_spinlock is acquired before calling
usb_ep_queue() which causes a deadlock when dummy_hcd is being used.
This is because dummy_queue() callbacks into f_hidg_req_complete() which
tries to acquire the same spinlock. This is (part of) the backtrace when
the deadlock occurs:
0xffffffffc06b1410 in f_hidg_req_complete
0xffffffffc06a590a in usb_gadget_giveback_request
0xffffffffc06cfff2 in dummy_queue
0xffffffffc06a4b96 in usb_ep_queue
0xffffffffc06b1eb6 in f_hidg_write
0xffffffff8127730b in __vfs_write
0xffffffff812774d1 in vfs_write
0xffffffff81277725 in SYSC_write
Fix this by releasing the write_spinlock before calling usb_ep_queue()
Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com> Tested-by: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: stable@vger.kernel.org # 4.11+ Fixes: de9acb97c81e ("usb: gadget: f_hid: fix: Move IN request allocation to set_alt()") Signed-off-by: Radoslav Gerganov <rgerganov@vmware.com> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>