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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 47a055a..f8e7deb 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -356,10 +356,11 @@
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 @@
}
/* any errors get returned through the urb completion */
- local_irq_save (flags);
- spin_lock (&urb->lock);
+ spin_lock_irq(&hcd_root_hub_lock);
+ spin_lock(&urb->lock);
if (urb->status == -EINPROGRESS)
urb->status = status;
- spin_unlock (&urb->lock);
- usb_hcd_giveback_urb (hcd, urb);
- local_irq_restore (flags);
+ 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);
+ spin_lock(&hcd_root_hub_lock);
+
+ spin_unlock_irq(&hcd_root_hub_lock);
return 0;
}
@@ -559,8 +568,7 @@
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 @@
} 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 @@
{
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_unlock(&hcd_root_hub_lock);
+ usb_hcd_giveback_urb(hcd, urb);
+ spin_lock(&hcd_root_hub_lock);
+ }
+ }
+ spin_unlock_irqrestore(&hcd_root_hub_lock, flags);
return 0;
}