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Date: Thu, 26 Jul 2012 16:46:42 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/5] qom: adopt rwlock to protect accessing
 dev from removing it
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To: liu ping fan <qemulist@gmail.com>
Cc: kvm@vger.kernel.org, Stefan Hajnoczi <stefanha@gmail.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>, Jan Kiszka <jan.kiszka@siemens.com>, Paolo Bonzini <pbonzini@redhat.com>

On 07/26/2012 04:21 PM, liu ping fan wrote:
> On Thu, Jul 26, 2012 at 9:15 PM, Avi Kivity <avi@redhat.com> wrote:
>> On 07/26/2012 04:14 PM, liu ping fan wrote:
>>>>
>>>> From the description above, I don't see why it can't be a mutex.
>>>>
>>> Searching in the device tree (or MemoryRegion view) can be often in
>>> parallel, especially in mmio-dispatch code path
>>
>> In mmio dispatch we have a pointer to the object, we don't need to
>> search anything.  Is device tree search a hot path?
>>
> I think, we need lock to protect searching --phys_page_find()  from
> deleter--DeviceClass:unmap,  so rwlock?

Better a lock on phys_map (because it is easily replaced by rcu, later).

I think phys_map is also better isolated, so it will be easier to find
all the placed that need protection and to avoid deadlock.


-- 
error compiling committee.c: too many arguments to function