Re: [PATCH RFC tip/core/rcu 7/7] rcu: Quiet RCU-lockdep warningsinvolving interrupt disabling

[Yong Zhang]

On Tue, Dec 06, 2011 at 10:52:32AM +0100, Peter Zijlstra wrote:
> On Tue, 2011-12-06 at 09:26 +0800, Yong Zhang wrote:
> 
> > Yeah, because we call might_sleep() in rt_mutex_lock() unconditionally.
> > But in this case the 'BUG: sleeping function called from invalid context
> > at *' is obviously false positive.
> 
> Why can't this mutex acquisition not block?

It could block. The issue it's legal to call rt_mutex_lock() with
irqs disabled and we don't want might_sleep() bite us on this
special case. When we are going to sleep, we re-enable irq in
__rt_mutex_slowlock().

> 
> > Maybe we could teach might_sleep() about this special case?
> 
> Sounds horrid.

Maybe, any alternative?

Thanks,
Yong
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