On Wed, Nov 26, 2014 at 05:17:29PM +0200, Michael S. Tsirkin wrote: > 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. > Which is really the point of the patch you are trying to revert. That's assuming you disabled preemption. If you didn't, and take a spinlock, you have deadlocks even without userspace access. -- MST -- 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
