[07/12] usb: usbtest: use irqsave() in USB's complete callback

From: Alan Stern <stern@rowland.harvard.edu>
Date: 2018-06-25 15:15:06

On Mon, 25 Jun 2018, Sebastian Andrzej Siewior wrote:
quoted hunk
The USB completion callback does not disable interrupts while acquiring
the lock. We want to remove the local_irq_disable() invocation from
__usb_hcd_giveback_urb() and therefore it is required for the callback
handler to disable the interrupts while acquiring the lock.
The callback may be invoked either in IRQ or BH context depending on the
USB host controller.
Use the _irqsave() variant of the locking primitives.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/usb/misc/usbtest.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
index 9e1142b8b91b..3b56fb34906c 100644
--- a/drivers/usb/misc/usbtest.c
+++ b/drivers/usb/misc/usbtest.c
@@ -1082,11 +1082,12 @@ static void ctrl_complete(struct urb *urb)
 	struct usb_ctrlrequest	*reqp;
 	struct subcase		*subcase;
 	int			status = urb->status;
+	unsigned long		flags;
 
 	reqp = (struct usb_ctrlrequest *)urb->setup_packet;
 	subcase = container_of(reqp, struct subcase, setup);
 
-	spin_lock(&ctx->lock);
+	spin_lock_irqsave(&ctx->lock, flags);
 	ctx->count--;
 	ctx->pending--;
 
@@ -1152,9 +1153,9 @@ static void ctrl_complete(struct urb *urb)
 
 				if (u == urb || !u->dev)
 					continue;
-				spin_unlock(&ctx->lock);
+				spin_unlock_irqrestore(&ctx->lock, flags);
 				status = usb_unlink_urb(u);
-				spin_lock(&ctx->lock);
+				spin_lock_irqsave(&ctx->lock, flags);
My feeling tends to be that when a lock is temporarily dropped to take 
a single action like this, there's no need to restore the 
interrupt-enable flag.  These two calls can remain 
spin_unlock()/spin_lock().

Aside from this:

Acked-by: Alan Stern <stern@rowland.harvard.edu>

Alan Stern
---
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