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

On Wed, 29 Oct 2014, Jeff Kirsher wrote:

On Wed, 2014-10-29 at 20:36 +0100, Peter Zijlstra wrote:

quoted

On Wed, Oct 29, 2014 at 07:33:00PM +0100, Thomas Gleixner wrote:

quoted

Yuck. No. You are just papering over the problem.

What happens if you add 'threadirqs' to the kernel command line? Or if
the interrupt line is shared with a real threaded interrupt user?

The proper solution is to have a poll_lock for e1000 which serializes
the hardware interrupt against netpoll instead of using
disable/enable_irq().

In fact that's less expensive than the disable/enable_irq() dance and
the chance of contention is pretty low. If done right it will be a
NOOP for the CONFIG_NET_POLL_CONTROLLER=n case.

OK a little something like so then I suppose.. But I suspect most all
the network drivers will need this and maybe more, disable_irq() is a
popular little thing and we 'just' changed semantics on them.

Thomas- if you are fine with Peter's patch, I can get this under
testing.

I'm fine with it except for the comment part of disable_irq(), but
that does not matter :)

One nitpick: Instead of having the lock unconditionally, I'd make it
depend on CONFIG_NET_POLL_CONTROLLER.

#ifdef CONFIG_NET_POLL_CONTROLLER
static inline void netpoll_lock(struct e1000_adapter *adapter)
{
	spin_lock(&adapter->irq_lock);
}

static inline void netpoll_unlock(struct e1000_adapter *adapter)
{
	spin_unlock(&adapter->irq_lock);
}
#else
static inline void netpoll_lock(struct e1000_adapter *adapter) { }
static inline void netpoll_unlock(struct e1000_adapter *adapter) { }
#endif

and use that instead of the unconditional spin[un]lock() invocations.

But that's up to you.

Thanks,

	tglx