Am Samstag, 16. April 2005 00:53 schrieb David Brownell:
> > > > Auditing locking in all drivers is not.
> > > > Switching to tasklets would result in revisting locking in drivers.
> > >
> > > Why would switching uhci-hcd over to a tasklet require any change in
> > > other
> > > drivers?
> >
> > You have to audit all drivers to check them for synchronization between
> > the callback and other hard irqs. In addition to reap the full benefit from
> > a switch to tasklets, you'd have to change the drivers to use
> > spin_lock_bh().
>
> Not many USB device driver use tasklets, but all those would need to be
> audited/modified.
Not quite so simple. Have a look at this code from message.c:
static void sg_complete (struct urb *urb, struct pt_regs *regs)
{
struct usb_sg_request *io = (struct usb_sg_request *) urb->context;
spin_lock (&io->lock);
This is equivalent to spin_lock_irqsave if called from hard irq. In a tasklet
it is spin_lock_bh. Do you know whether io->lock is ever taken in hard irq?
You need to find out. Simply taking _irqsave would counter the purpose of
switching to a tasklet.
Regards
Oliver
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