Re: [RFC PATCH v2 3/8] block: introduce a lock to protect graph operations

[Paolo Bonzini]

On 4/26/22 10:51, Emanuele Giuseppe Esposito wrote:
> If a coroutine changes AioContext, the counter in the original and new
> AioContext are left intact, since the writer does not care where is the
> reader, but only if there is one.

"As a result, some AioContexts might have a negative reader count, to 
balance the positive count of the AioContext that took the lock.  This 
also means that when an AioContext is deleted it may have a nonzero 
reader count.  In that case we transfer the count to a global shared 
counter..."

Paolo

> If instead the original AioContext gets deleted, we need to transfer the
> current amount of readers in a global shared counter, so that the writer
> is always aware of all readers.