Am 26.11.2014 um 16:17 schrieb Michael S. Tsirkin: > On Wed, Nov 26, 2014 at 11:05:04AM +0100, David Hildenbrand wrote: >>> What's the path you are trying to debug? >> >> Well, we had a problem where we held a spin_lock and called >> copy_(from|to)_user(). We experienced very random deadlocks that took some guy >> almost a week to debug. The simple might_sleep() check would have showed this >> error immediately. > > This must have been a very old kernel. > A modern kernel will return an error from copy_to_user. I disagree. copy_to_user will not return while holding a spinlock, because it does not know! How should it? See: spin_lock will call preempt_disable, but thats a no-op for a non-preempt kernel. So the mere fact that we hold a spin_lock is not known by any user access function. (or others). No? Christian -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
