Messages in this thread | | | Date | Wed, 29 Oct 2014 21:07:13 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: e1000_netpoll(): disable_irq() triggers might_sleep() on linux-next |
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On Wed, 29 Oct 2014, Peter Zijlstra wrote:
> On Wed, Oct 29, 2014 at 08:49:03PM +0100, Thomas Gleixner wrote: > > On Wed, 29 Oct 2014, Peter Zijlstra wrote: > > > > > On Wed, Oct 29, 2014 at 07:33:00PM +0100, Thomas Gleixner wrote: > > > > 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. > > > > We changed that almost 4 years ago :) What we 'just' did was to add a > > prominent warning into the code. > > You know that is the same right... they didn't know it was broken > therefore it wasn't :-), but now they need to go actually do stuff about > it, an entirely different proposition.
Right, and of course the world and some more has the very same code there:
poll_controller() { disable_irq(); dev_interrupt_handler(); enable_irq(); }
Trying to twist my brain to come up with a solution which avoids the spinlock, but I have a hard time to come up with one.
The only thing I came up with so far is to avoid adding locks to every driver incarnation and instead put it into struct net_device and provide helper functions for the lock/unlock case.
That does not change the fact that we need to deal with that on a per driver basis :(
Thanks,
tglx
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