Re: [PATCH v2 6/7] block-copy: atomic .cancelled and .finished fields in BlockCopyCallState

[Paolo Bonzini]

On 20/05/21 17:34, Vladimir Sementsov-Ogievskiy wrote:
> > By adding acquire/release pairs, we ensure that .ret and .error_is_read
> > fields are written by block_copy_dirty_clusters before .finished is true.
>
> As I already said, please, can we live with one mutex for now? finished, 
> ret, error_is_read, all these variables are changing rarely. I doubt 
> that performance is improved by these atomic operations. But complexity 
> of the architecture increases exponentially.

The problem is that these are used outside coroutines. 
load-acquire/store-release is the simplest way to handle a "finished" 
flag really.

Paolo