[PATCH] USB: Simplify locking in UHCI

This patch is an amalgam of 9 contributions from Stephen Hemminger.  It
begins the process of straightening out the use of semaphores and locking
in the UHCI driver by removing unneeded irqsaves and irqrestores.  It
also removes an unnecessary list node and makes a couple of other small
changes.



clear_next_interrupt only called in IRQ context don't need irqsave/restore

Since uhci_finish_completion is only called from IRQ routine,
the irqsave/irqrestore is redundant and unnecessary.

UHCI transfer_result is only called from IRQ context
so irqsave/restore is unnecessary here.

uhci_finish_urb is always called from irq so
no need for irqsave/irqrestore.

uhci_add_complete only called from IRQ context

The complete_list element in the urb private data is redundant,
since it is only used when the urb is on the complete list.
And given the state transitions, an urb can't be on the complete list
and any other list (remove, or urb_list).
Therefore just use urb_list to link the complete_list

Use list_move_tail to move between remove (or urb_list) and the complete_list.

Save irq state in uhci_stop so that the irqsave/irqrestore's
in all the free_pending and remove_pending code can be eliminated.

Since uhci_stop now saves IRQ state, the free/remove pending routines
no longer need irqsave/irqrestore.

drivers/usb/host/uhci-debug.c

@@ -402,7 +402,7 @@ static int uhci_show_lists(struct uhci_hcd *uhci, char *buf, int len)
 		head = &uhci->complete_list;
 		tmp = head->next;
 		while (tmp != head) {
-			struct urb_priv *urbp = list_entry(tmp, struct urb_priv, complete_list);
+			struct urb_priv *urbp = list_entry(tmp, struct urb_priv, urb_list);
 
 			out += sprintf(out, "  %d: ", ++count);
 			out += uhci_show_urbp(uhci, urbp, out, len - (out - buf));

drivers/usb/host/uhci-hcd.c

@@ -122,21 +122,17 @@ static inline void uhci_set_next_interrupt(struct uhci_hcd *uhci)
 
 static inline void uhci_clear_next_interrupt(struct uhci_hcd *uhci)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&uhci->frame_list_lock, flags);
+	spin_lock(&uhci->frame_list_lock);
 	uhci->term_td->status &= ~cpu_to_le32(TD_CTRL_IOC);
-	spin_unlock_irqrestore(&uhci->frame_list_lock, flags);
+	spin_unlock(&uhci->frame_list_lock);
 }
 
-static inline void uhci_add_complete(struct uhci_hcd *uhci, struct urb *urb)
+static inline void uhci_moveto_complete(struct uhci_hcd *uhci, 
+					struct urb_priv *urbp)
 {
-	struct urb_priv *urbp = (struct urb_priv *)urb->hcpriv;
-	unsigned long flags;
-
-	spin_lock_irqsave(&uhci->complete_list_lock, flags);
-	list_add_tail(&urbp->complete_list, &uhci->complete_list);
-	spin_unlock_irqrestore(&uhci->complete_list_lock, flags);
+	spin_lock(&uhci->complete_list_lock);
+	list_move_tail(&urbp->urb_list, &uhci->complete_list);
+	spin_unlock(&uhci->complete_list_lock);
 }
 
 static struct uhci_td *uhci_alloc_td(struct uhci_hcd *uhci, struct usb_device *dev)
@@ -672,7 +668,6 @@ static struct urb_priv *uhci_alloc_urb_priv(struct uhci_hcd *uhci, struct urb *u
 	
 	INIT_LIST_HEAD(&urbp->td_list);
 	INIT_LIST_HEAD(&urbp->queue_list);
-	INIT_LIST_HEAD(&urbp->complete_list);
 	INIT_LIST_HEAD(&urbp->urb_list);
 
 	list_add_tail(&urbp->urb_list, &uhci->urb_list);
@@ -723,9 +718,6 @@ static void uhci_destroy_urb_priv(struct uhci_hcd *uhci, struct urb *urb)
 	if (!list_empty(&urbp->urb_list))
 		warn("uhci_destroy_urb_priv: urb %p still on uhci->urb_list or uhci->remove_list", urb);
 
-	if (!list_empty(&urbp->complete_list))
-		warn("uhci_destroy_urb_priv: urb %p still on uhci->complete_list", urb);
-
 	spin_lock_irqsave(&uhci->td_remove_list_lock, flags);
 
 	/* Check to see if the remove list is empty. Set the IOC bit */
@@ -1533,10 +1525,9 @@ static int uhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, int mem_flags)
 static void uhci_transfer_result(struct uhci_hcd *uhci, struct urb *urb)
 {
 	int ret = -EINPROGRESS;
-	unsigned long flags;
 	struct urb_priv *urbp;
 
-	spin_lock_irqsave(&urb->lock, flags);
+	spin_lock(&urb->lock);
 
 	urbp = (struct urb_priv *)urb->hcpriv;
 
@@ -1591,13 +1582,11 @@ static void uhci_transfer_result(struct uhci_hcd *uhci, struct urb *urb)
 			usb_pipetype(urb->pipe), urb);
 	}
 
-	/* Remove it from uhci->urb_list */
-	list_del_init(&urbp->urb_list);
-
-	uhci_add_complete(uhci, urb);
+	/* Move it from uhci->urb_list to uhci->complete_list */
+	uhci_moveto_complete(uhci, urbp);
 
 out:
-	spin_unlock_irqrestore(&urb->lock, flags);
+	spin_unlock(&urb->lock);
 }
 
 /*
@@ -1796,9 +1785,8 @@ static int init_stall_timer(struct usb_hcd *hcd)
 static void uhci_free_pending_qhs(struct uhci_hcd *uhci)
 {
 	struct list_head *tmp, *head;
-	unsigned long flags;
 
-	spin_lock_irqsave(&uhci->qh_remove_list_lock, flags);
+	spin_lock(&uhci->qh_remove_list_lock);
 	head = &uhci->qh_remove_list;
 	tmp = head->next;
 	while (tmp != head) {
@@ -1810,15 +1798,14 @@ static void uhci_free_pending_qhs(struct uhci_hcd *uhci)
 
 		uhci_free_qh(uhci, qh);
 	}
-	spin_unlock_irqrestore(&uhci->qh_remove_list_lock, flags);
+	spin_unlock(&uhci->qh_remove_list_lock);
 }
 
 static void uhci_free_pending_tds(struct uhci_hcd *uhci)
 {
 	struct list_head *tmp, *head;
-	unsigned long flags;
 
-	spin_lock_irqsave(&uhci->td_remove_list_lock, flags);
+	spin_lock(&uhci->td_remove_list_lock);
 	head = &uhci->td_remove_list;
 	tmp = head->next;
 	while (tmp != head) {
@@ -1830,17 +1817,16 @@ static void uhci_free_pending_tds(struct uhci_hcd *uhci)
 
 		uhci_free_td(uhci, td);
 	}
-	spin_unlock_irqrestore(&uhci->td_remove_list_lock, flags);
+	spin_unlock(&uhci->td_remove_list_lock);
 }
 
 static void uhci_finish_urb(struct usb_hcd *hcd, struct urb *urb, struct pt_regs *regs)
 {
 	struct uhci_hcd *uhci = hcd_to_uhci(hcd);
-	unsigned long flags;
 
-	spin_lock_irqsave(&urb->lock, flags);
+	spin_lock(&urb->lock);
 	uhci_destroy_urb_priv(uhci, urb);
-	spin_unlock_irqrestore(&urb->lock, flags);
+	spin_unlock(&urb->lock);
 
 	usb_hcd_giveback_urb(hcd, urb, regs);
 }
@@ -1849,44 +1835,40 @@ static void uhci_finish_completion(struct usb_hcd *hcd, struct pt_regs *regs)
 {
 	struct uhci_hcd *uhci = hcd_to_uhci(hcd);
 	struct list_head *tmp, *head;
-	unsigned long flags;
 
-	spin_lock_irqsave(&uhci->complete_list_lock, flags);
+	spin_lock(&uhci->complete_list_lock);
 	head = &uhci->complete_list;
 	tmp = head->next;
 	while (tmp != head) {
-		struct urb_priv *urbp = list_entry(tmp, struct urb_priv, complete_list);
+		struct urb_priv *urbp = list_entry(tmp, struct urb_priv, urb_list);
 		struct urb *urb = urbp->urb;
 
-		list_del_init(&urbp->complete_list);
-		spin_unlock_irqrestore(&uhci->complete_list_lock, flags);
+		list_del_init(&urbp->urb_list);
+		spin_unlock(&uhci->complete_list_lock);
 
 		uhci_finish_urb(hcd, urb, regs);
 
-		spin_lock_irqsave(&uhci->complete_list_lock, flags);
+		spin_lock(&uhci->complete_list_lock);
 		head = &uhci->complete_list;
 		tmp = head->next;
 	}
-	spin_unlock_irqrestore(&uhci->complete_list_lock, flags);
+	spin_unlock(&uhci->complete_list_lock);
 }
 
 static void uhci_remove_pending_urbps(struct uhci_hcd *uhci)
 {
 	struct list_head *tmp, *head;
-	unsigned long flags;
 
-	spin_lock_irqsave(&uhci->urb_remove_list_lock, flags);
+	spin_lock(&uhci->urb_remove_list_lock);
 	head = &uhci->urb_remove_list;
 	tmp = head->next;
 	while (tmp != head) {
 		struct urb_priv *urbp = list_entry(tmp, struct urb_priv, urb_list);
-		struct urb *urb = urbp->urb;
 
 		tmp = tmp->next;
-		list_del_init(&urbp->urb_list);
-		uhci_add_complete(uhci, urb);
+		uhci_moveto_complete(uhci, urbp);
 	}
-	spin_unlock_irqrestore(&uhci->urb_remove_list_lock, flags);
+	spin_unlock(&uhci->urb_remove_list_lock);
 }
 
 static irqreturn_t uhci_irq(struct usb_hcd *hcd, struct pt_regs *regs)
@@ -2434,6 +2416,7 @@ static int uhci_start(struct usb_hcd *hcd)
 static void uhci_stop(struct usb_hcd *hcd)
 {
 	struct uhci_hcd *uhci = hcd_to_uhci(hcd);
+	unsigned long flags;
 
 	del_timer_sync(&uhci->stall_timer);
 
@@ -2441,6 +2424,7 @@ static void uhci_stop(struct usb_hcd *hcd)
 	 * At this point, we're guaranteed that no new connects can be made
 	 * to this bus since there are no more parents
 	 */
+	local_irq_save(flags);
 	uhci_free_pending_qhs(uhci);
 	uhci_free_pending_tds(uhci);
 	uhci_remove_pending_urbps(uhci);
@@ -2449,6 +2433,7 @@ static void uhci_stop(struct usb_hcd *hcd)
 
 	uhci_free_pending_qhs(uhci);
 	uhci_free_pending_tds(uhci);
+	local_irq_restore(flags);
 	
 	release_uhci(uhci);
 }

drivers/usb/host/uhci-hcd.h

@@ -387,7 +387,6 @@ struct urb_priv {
 	unsigned long fsbrtime;		/* In jiffies */
 
 	struct list_head queue_list;	/* P: uhci->frame_list_lock */
-	struct list_head complete_list;	/* P: uhci->complete_list_lock */
 };
 
 /*