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Re: [Qemu-devel] [big lock] Discussion about the convention of device's
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock |
Date: |
Wed, 19 Sep 2012 12:23:24 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 |
On 09/19/2012 12:19 PM, liu ping fan wrote:
> On Wed, Sep 19, 2012 at 5:14 PM, Paolo Bonzini <address@hidden> wrote:
>> Il 19/09/2012 11:11, liu ping fan ha scritto:
>>>> > Why not? devA will drop its local lock, devX will retake the big lock
>>>> > recursively, devB will take its local lock. In the end, we have biglock
>>>> > -> devB.
>>>> >
>>> But when adopting local lock, we assume take local lock, then biglock.
>>
>> No, because the local lock will be dropped before taking the biglock.
>> The order must always be coarse->fine.
>>
> But if we takes coarse firstly, then the mmio-dispatcher will still
> contend for the big lock against each other.
Can you detail the sequence?
>
>> I don't know if the front-end (device) lock should come before or after
>> the back-end (e.g. netdev) lock in the hierarchy, but that's another story.
>>
> I think fine->coarse may be the rule, since for some code path, it is
> not necessary to take coarse lock.
coarse->fine doesn't mean you have to take the coarse lock.
Valid:
lock(coarse)
lock(fine)
Valid:
lock(find)
Valid:
lock(coarse)
Invalid:
lock(fine)
lock(coarse)
--
error compiling committee.c: too many arguments to function
- [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/18
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Paolo Bonzini, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock,
Avi Kivity <=
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Jan Kiszka, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Jan Kiszka, 2012/09/19
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/20
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Paolo Bonzini, 2012/09/20
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/20
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Paolo Bonzini, 2012/09/20
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Avi Kivity, 2012/09/20
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, liu ping fan, 2012/09/21
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Paolo Bonzini, 2012/09/21
- Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock, Avi Kivity, 2012/09/19