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Date: Thu, 23 Jul 2015 20:59:14 +0800
From: Wen Congyang <ghostwcy@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] rcu: actually register threads that have
 RCU read-side critical sections
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To: Paolo Bonzini <pbonzini@redhat.com>, Wen Congyang <wency@cn.fujitsu.com>, Christian Borntraeger <borntraeger@de.ibm.com>, qemu-devel@nongnu.org

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
>
>