On Fri, Mar 27, 2009 at 05:18:18PM +0200, Darius Augulis wrote: > > You use an FIQ for SoF, and spin_lock_irqsave() to protect. Don't they > > only disable IRQs and not FIQs? But it seems your FIQ cannot cause any > > trouble, so, it should be fine. Do you really need an FIQ? This is precisely the area where FIQs can't be used. You can't take spinlocks (even IRQ-safe spinlocks) from FIQs. Why? You'll deadlock. Consider: spin_lock_irqsave(lock, flags); ... FIQ happens FIQ: spin_lock_irqsave(lock, flags); <=== deadlock And there's nothing you can do about that. And no, converting this locking primitive to also disable FIQs means that then FIQs will be subject to the same latency as normal IRQs. In fact, in uniprocessor mode, you might as well completely forget the spinlock, because the lock part is a no-op, and the IRQ disable has no effect on FIQs. If you're going to be using FIQs in C code, you need to be _very_ _very_ careful about what you do. Calling normal kernel functions is generally not going to be safe in any way. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
