Re: RCU stall in af_unix.c, should use spin_lock_irqsave?

Eric Dumazet
2014-10-21T10:28:24Z

On Tue, 2014-10-21 at 12:10 +0200, Thomas Petazzoni wrote:

> Ok. So it's actually safe to mix spin_lock() and spin_lock_irqsave() on
> the same lock, if you know that this lock will never ever be taken in
> an interrupt context?

Sure.

>
> > mvpp2 is seriously brain damaged : on_each_cpu() cannot be used from
> > a bottom half handler.
>
> That's what I thought. Back to the drawing board then, to fix mvpp2.
>
> Do you think there is a place where we can write down those
> assumptions? It isn't easy to spot whether on_each_cpu() is safe to use
> in a bottom half or not.
>

Really ? kernel/smp.c is full of comments.

Too many comments and people seem to not read them ;)

Take a look at smp_call_function(), which is called from on_each_cpu()