Re: e1000_netpoll(): disable_irq() triggers might_sleep() on linux-next

On Wed, 29 Oct 2014, Peter Zijlstra wrote:

On Wed, Oct 29, 2014 at 09:23:42PM +0100, Thomas Gleixner wrote:

quoted

But at least it allows to mitigate the impact by making it conditional
at a central point.

static inline void netpoll_lock(struct net_device *nd)
{
	if (netpoll_active(nd))
		spin_lock(&nd->netpoll_lock);
}

branch fail vs lock might be a toss on most machines, but if we're
hitting cold cachelines we loose big.

Well, if the net_device is not cache hot on irq entry you have lost
already. The extra branch/lock is not going to add much to that.
 
Thanks,

	tglx