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()
Signed-off-by: Radoslav Gerganov <rgerganov@xxxxxxxxxx>
Reviewed-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Tested-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.11+
Fixes: 749494b6bdbb ("usb: gadget: f_hid: fix: Move IN request allocation to set_alt()")
---
In v2 only the commit message is changed.
---
drivers/usb/gadget/function/f_hid.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index 54e859d..492bb44 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -391,20 +391,20 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
req->complete = f_hidg_req_complete;
req->context = hidg;
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+
status = usb_ep_queue(hidg->in_ep, req, GFP_ATOMIC);
if (status < 0) {
ERROR(hidg->func.config->cdev,
"usb_ep_queue error on int endpoint %zd\n", status);
- goto release_write_pending_unlocked;
+ goto release_write_pending;
} else {
status = count;
}
- spin_unlock_irqrestore(&hidg->write_spinlock, flags);
return status;
release_write_pending:
spin_lock_irqsave(&hidg->write_spinlock, flags);
-release_write_pending_unlocked:
hidg->write_pending = 0;
spin_unlock_irqrestore(&hidg->write_spinlock, flags);
--
1.9.1
