Message-ID: <538DCF15.4080904@gmail.com>
Date: Tue, 03 Jun 2014 09:35:17 -0400
From: Vlad Yasevich <vyasevich@gmail.com>
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To: Paolo Bonzini <pbonzini@redhat.com>, Eric Dumazet <eric.dumazet@gmail.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
CC: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        David Miller <davem@davemloft.net>
Subject: Re: [PULL 2/2] vhost: replace rcu with mutex
References: <1401744482-17764-1-git-send-email-mst@redhat.com>	<1401744482-17764-3-git-send-email-mst@redhat.com> <1401746280.3645.187.camel@edumazet-glaptop2.roam.corp.google.com> <538DC422.1050303@redhat.com>
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On 06/03/2014 08:48 AM, Paolo Bonzini wrote:
> Il 02/06/2014 23:58, Eric Dumazet ha scritto:
>> This looks dubious
>>
>> What about using kfree_rcu() instead ?
> 
> It would lead to unbound allocation from userspace.
> 
>> translate_desc() still uses rcu_read_lock(), its not clear if the mutex
>> is really held.
> 
> Yes, vhost_get_vq_desc must be called with the vq mutex held.
> 
> The rcu_read_lock/unlock in translate_desc is unnecessary.
> 

If that's true, then does dev->memory really needs to be rcu protected?
It appears to always be read under mutex.

-vlad

> Paolo
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