Re: [Qemu-devel] [PATCH] rcu: actually register threads that have RCU read-side critical sections

[Wen Congyang]

At 2015/7/23 19:08, Paolo Bonzini Wrote:
> On 23/07/2015 13:04, Wen Congyang wrote:
> > > Yes.  I think this is better for 2.4.  There are threads that do not
> > > need RCU, for example the thread-pool.c worker threads, so it may just
> >
> > If the thread doesn't use RCU, rcu_register_thread() is harmless, is it right?
>
> Every rcu_register_thread() makes synchronize_rcu() a little slower.

Yes, but synchronize_rcu() is very slow...

> > > > be simpler to add an assertion in rcu_register_thread.  I'm just a bit
> > > > wary of doing little more than the bare minimum in 2.4, because of the
> > > > OS X failure that I didn't quite understand.
> > Which problem? I don't find it in the maillist.
>
> http://article.gmane.org/gmane.comp.emulators.qemu/351548

Hmm, I guess rcu_reader is invalid when pthread key is destroyed. 
pthread key and __thread
variable, which is destroyed first? I don't find any document to 
describe it.

Thanks
Wen Congyang

> Paolo