Question about change to ehci-hcd

Dave:

While going through ehci-hcd, I came up with this:

Index: usb-2.6/drivers/usb/host/ehci-q.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci-q.c
+++ usb-2.6/drivers/usb/host/ehci-q.c
@@ -282,7 +282,7 @@ static int qh_schedule (struct ehci_hcd 
 static unsigned
 qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
 {
-	struct ehci_qtd		*last = NULL, *end = qh->dummy;
+	struct ehci_qtd		*last = NULL;
 	struct list_head	*entry, *tmp;
 	int			stopped;
 	unsigned		count = 0;
@@ -330,8 +330,8 @@ qh_completions (struct ehci_hcd *ehci, s
 			last = NULL;
 		}
 
-		/* ignore urbs submitted during completions we reported */
-		if (qtd == end)
+		/* stop when we reach the dummy at the end */
+		if (qtd == qh->dummy)
 			break;
 
 		/* hardware copies qtd out of qh overlay */

It looks like the original code has a mistaken optimization there.  If 
during a callback some driver submitted an URB and then unlinked it, 
the unlink would effectively get lost.

Alan Stern


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