Commit 9439eb94 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
Browse files

USB: update spinlock usage for root-hub URBs 



This patch (as952) adjusts the spinlock usage in the root-hub
emulation part of usbcore, to make it match more closely the pattern
used by regular host controller drivers.  To wit: The private lock
(usb_hcd_root_hub_lock) is held throughout the important parts, and it
is dropped temporarily without re-enabling interrupts around the call
to usb_hcd_giveback_urb().

A nice side effect is that the code now avoids calling
local_irq_save(), thereby becoming more RT-friendly.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent d617bc83

drivers/usb/core/hcd.c

+29 −23
Original line number Diff line number Diff line
@@ -356,10 +356,11 @@ static int rh_call_control (struct usb_hcd *hcd, struct urb *urb) 
	const u8	*bufp = tbuf;

	int		len = 0;

	int		patch_wakeup = 0;

	unsigned long	flags;

	int		status = 0;

	int		n;



	might_sleep();



	cmd = (struct usb_ctrlrequest *) urb->setup_packet;

	typeReq  = (cmd->bRequestType << 8) | cmd->bRequest;

	wValue   = le16_to_cpu (cmd->wValue);
@@ -523,13 +524,21 @@ error: 
	}



	/* any errors get returned through the urb completion */

	local_irq_save (flags);

	spin_lock_irq(&hcd_root_hub_lock);

	spin_lock(&urb->lock);

	if (urb->status == -EINPROGRESS)

		urb->status = status;

	spin_unlock(&urb->lock);



	/* This peculiar use of spinlocks echoes what real HC drivers do.

	 * Avoiding calls to local_irq_disable/enable makes the code

	 * RT-friendly.

	 */

	spin_unlock(&hcd_root_hub_lock);

	usb_hcd_giveback_urb(hcd, urb);

	local_irq_restore (flags);

	spin_lock(&hcd_root_hub_lock);



	spin_unlock_irq(&hcd_root_hub_lock);

	return 0;

}
@@ -559,8 +568,7 @@ void usb_hcd_poll_rh_status(struct usb_hcd *hcd) 
	if (length > 0) {



		/* try to complete the status urb */

		local_irq_save (flags);

		spin_lock(&hcd_root_hub_lock);

		spin_lock_irqsave(&hcd_root_hub_lock, flags);

		urb = hcd->status_urb;

		if (urb) {

			spin_lock(&urb->lock);
@@ -574,16 +582,16 @@ void usb_hcd_poll_rh_status(struct usb_hcd *hcd) 
			} else		/* urb has been unlinked */

				length = 0;

			spin_unlock(&urb->lock);



			spin_unlock(&hcd_root_hub_lock);

			usb_hcd_giveback_urb(hcd, urb);

			spin_lock(&hcd_root_hub_lock);

		} else

			length = 0;

		spin_unlock(&hcd_root_hub_lock);



		/* local irqs are always blocked in completions */

		if (length > 0)

			usb_hcd_giveback_urb (hcd, urb);

		else

		if (length <= 0)

			hcd->poll_pending = 1;

		local_irq_restore (flags);

		spin_unlock_irqrestore(&hcd_root_hub_lock, flags);

	}



	/* The USB 2.0 spec says 256 ms.  This is close enough and won't
@@ -651,25 +659,23 @@ static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb) 
{

	unsigned long	flags;



	spin_lock_irqsave(&hcd_root_hub_lock, flags);

	if (usb_endpoint_num(&urb->ep->desc) == 0) {	/* Control URB */

		;	/* Do nothing */



	} else {				/* Status URB */

		if (!hcd->uses_new_polling)

			del_timer (&hcd->rh_timer);

		local_irq_save (flags);

		spin_lock (&hcd_root_hub_lock);

		if (urb == hcd->status_urb) {

			hcd->status_urb = NULL;

			urb->hcpriv = NULL;

		} else

			urb = NULL;		/* wasn't fully queued */



			spin_unlock(&hcd_root_hub_lock);

		if (urb)

			usb_hcd_giveback_urb(hcd, urb);

		local_irq_restore (flags);

			spin_lock(&hcd_root_hub_lock);

		}



	}

	spin_unlock_irqrestore(&hcd_root_hub_lock, flags);

	return 0;

}

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