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Message-ID: <4e777ed10706151103w35ae4acv149d82aba0b59775@mail.gmail.com> Date: Fri, 15 Jun 2007 14:03:05 -0400 From: "Zhu Han" <schumi.han@...il.com> To: "Kieran Mansley" <kmansley@...arflare.com> Cc: xen-devel@...ts.xensource.com, netdev@...r.kernel.org, herbert@...dor.apana.org.au Subject: Re: [Xen-devel] [PATCH 4/4] [Net] Support accelerated network plugin modules On 6/15/07, Kieran Mansley <kmansley@...arflare.com> wrote: > > The lock protects the use_count variable. The use_count variable > prevents the plugin module unloading while it is being used. I couldn't > just use the lock to prevent the module unloading as the hook function > (i) might block (and holding a spin_lock would be rather antisocial) > (ii) might call back into netfront and try to take the lock again, which > would deadlock. > If the hook routine blocks on the other code path instead of tx/rx path, why not use a simple atomic reference count. When the reference count reachs zero, free it. Considering you can synchronzie on tx/rx path, the free will not happen under the critical code path. So the uninitialize work could be done inside the free routine even if it blocks. >I think that RCU would only work in this situation if the hook functions >didn't block,. I agree. > > Kieran > > > > > > -- best regards, hanzhu - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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