USB: usb serial gadget smp related bug

Adjust dev->dev_lock spinlock lock/unlock calls to be safe for SMP case.
Otherwise the following sequence may lead to a deadlock in SMP case:

gs_send()->usb_ep_queue()
	->(in case a request is satisfied immediatly) gs_write_complete()

for ex for pxa2xx_udc.c: 
usb_ep_queue()->pxa2xx_ep_queue()->write_fifo()->done()->gs_write_complete() 
(through req.complete pointer)

Signed-off-by: Eugeny S. Mints <emints@ru.mvista.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/usb/gadget/serial.c b/drivers/usb/gadget/serial.c
index e762aa19ab0a..b893e3118e1b 100644
--- a/drivers/usb/gadget/serial.c
+++ b/drivers/usb/gadget/serial.c
@@ -1120,12 +1120,15 @@ static int gs_send(struct gs_dev *dev)
 gs_debug_level(3, "gs_send: len=%d, 0x%2.2x 0x%2.2x 0x%2.2x ...\n", len, *((unsigned char *)req->buf), *((unsigned char *)req->buf+1), *((unsigned char *)req->buf+2));
                         list_del(&req_entry->re_entry);
                         req->length = len;
+                        spin_unlock_irqrestore(&dev->dev_lock, flags);
                         if ((ret=usb_ep_queue(ep, req, GFP_ATOMIC))) {
                                 printk(KERN_ERR
                                 "gs_send: cannot queue read request, ret=%d\n",
                                         ret);
+                                spin_lock_irqsave(&dev->dev_lock, flags);
                                 break;
                         }
+                        spin_lock_irqsave(&dev->dev_lock, flags);
                 } else {
                         break;
                 }