On Wed, 22 Feb 2012, Sebastian Andrzej Siewior wrote: > The kernel doc entry for usb_unlink_urb() contains the phrase "This > request is always asynchronous.". The "always" leads to the assumption > that the ->complete() callback is not called from within > usb_unlink_urb(). This is not true. The HCD is allowed to call the > ->complete() from within ->urb_dequeue() if it is appropriate for the > hardware. > This patch updates the kernel doc so usb-device driver authors make sure > to drop all locks (and make sure it is okay to drop them) which are > acquired by the complete callback before calling usb_unlink_urb(). > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > --- > drivers/usb/core/urb.c | 9 +++++---- > 1 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c > index f4f20c7..d72b376 100644 > --- a/drivers/usb/core/urb.c > +++ b/drivers/usb/core/urb.c > @@ -527,10 +527,11 @@ EXPORT_SYMBOL_GPL(usb_submit_urb); > * a driver's I/O routines to insure that all URB-related activity has > * completed before it returns. > * > - * This request is always asynchronous. Success is indicated by > - * returning -EINPROGRESS, at which time the URB will probably not yet > - * have been given back to the device driver. When it is eventually > - * called, the completion function will see @urb->status == -ECONNRESET. > + * This request is asynchronous, however the hcd might call the ->complete() > + * callback during unlink. "Therefore when drivers call usb_unlink_urb(), they must not hold any locks that may be taken by the completion function." Also, we write "HCD" in capital letters. > Success is indicated by returning -EINPROGRESS, at > + * which time the URB will probably not yet have been given back to the device > + * driver. When it is eventually called, the completion function will see > + * @urb->status == -ECONNRESET. > * Failure is indicated by usb_unlink_urb() returning any other value. > * Unlinking will fail when @urb is not currently "linked" (i.e., it was > * never submitted, or it was unlinked before, or the hardware is already Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
