lkml.org 
[lkml]   [2007]   [Oct]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
SubjectUSB HCD: avoid duplicate local_irq_disable()
Date
usb_hcd_flush_endpoint() has a retry loop that starts with a spin_lock_irq(),
but only gives up the spinlock, not the irq_disable before jumping to the
rescan label.

Split the spin_lock_irq into the retryable part and the local_irq_disable()
that is only done once as a micro-optimization and slight cleanup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
On Tuesday 23 October 2007, I wrote:
> I tried the trivial annotation below and (with lockdep enabled) got a few
> warnings at boot time, but only one that I could still find in the log
> buffer:

One more such example that was not found by lockdep. I guess this counts
as a false positive, as it is clearly harmless, but working around
it is a small optimization for the case where local_irq_disable()
is a hypervisor call.

Should we try to fix this class of (non-)problem in other places?
Will this patch cause a different warning with lockdep since now we
are pairing spin_lock() with spin_unlock_irq()?

--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1312,8 +1312,9 @@ void usb_hcd_flush_endpoint(struct usb_device *udev,
hcd = bus_to_hcd(udev->bus);

/* No more submits can occur */
+ local_irq_disable();
rescan:
- spin_lock_irq(&hcd_urb_list_lock);
+ spin_lock(&hcd_urb_list_lock);
list_for_each_entry (urb, &ep->urb_list, urb_list) {
int is_in;

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-10-23 03:31    [from the cache]
©2003-2011 Jasper Spaans. Advertise on this site