Re: [RFC PATCH v4 2/5] ramlist mutex

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On 08/23/2011 11:17 AM, Marcelo Tosatti wrote:
>  >    typedef struct RAMList {
>  >  +    QemuMutex mutex;
>  >        uint8_t *phys_dirty;
>  >        QLIST_HEAD(ram, RAMBlock) blocks;
>  >        QLIST_HEAD(, RAMBlock) blocks_mru;
>
>  A comment on what the mutex protects would be good.

Indeed, especially because Umesh wanted to use the ramlist+iothread combo as a rw-lock: iothread = read-lock for the I/O thread, ramlist = read-lock for the migration thread, together = exclusive (write) lock. But I think I talked him out of this. :) It's not a bad idea in general, it just sounds like overkill in this case.

And on the lock ordering.

I think when only two locks are involved, we can always assume iothread is outer and the other is inner. Do you agree?

Paolo
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