From stern@rowland.harvard.edu Thu Aug 2 14:25:24 2007 From: Alan Stern Date: Thu, 2 Aug 2007 15:05:45 -0400 (EDT) Subject: [PATCH 2/3] USB: update spinlock usage for root-hub URBs To: Greg KH Message-ID: 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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hcd.c | 52 +++++++++++++++++++++++++++---------------------- 1 file changed, 29 insertions(+), 23 deletions(-) --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -356,10 +356,11 @@ static int rh_call_control (struct usb_h 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 (&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 @@ void usb_hcd_poll_rh_status(struct usb_h 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_h } 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 us { 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; }