On Wed, Jun 24, 2015 at 10:47:47AM +0800, Fam Zheng wrote: > On Tue, 06/16 17:07, Stefan Hajnoczi wrote: > > On Tue, Jun 02, 2015 at 11:21:51AM +0800, Fam Zheng wrote: > > 2. Is this about thread safety? (No, it's about exclusive access to a > > BDS *within* the AioContext.) > > As it has to quiesce iothreads as well (for now it's even more urgent than > exclusive access within the same AioContext), I'd rather take it as yes.
This mechanism is not about threads and it is also not thread-safe (the caller must acquire AioContext themselves). The mechanism is about notifying the users of a drive that no requests should be submitted. > BTW, is there any semantics in here that we can use for multiqueue block > layer? The callback to remove/add ioeventfd is needed by multiqueue in the same way as dataplane. I think the actual multiqueue I/O will need to be more fine-grained because the goal is to process I/O requests in parallel and independently. Multiqueue should not require exclusive access (which this mechanism provides) - that would defeat the point of multiqueue. Stefan
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