Re: [Qemu-devel] [PATCH v2 19/24] block: Allow wait_serialising_requests() at any point

[Wenchao Xia]

于 2013/12/13 21:22, Kevin Wolf 写道:
> We can only have a single wait_serialising_requests() call per request
> because otherwise we can run into deadlocks where requests are waiting
> for each other.
  do you mean:
mark_request_serialising(req)
...
wait_serialising_requests(req);
...
wait_serialising_requests(req);

 will have deadlock? I thought it is already resolved by patch 15?
Maybe here is another deadlock reason?

 The same is true when wait_serialising_requests() is not
> at the very beginning of a request, so that other requests can be issued
> between the start of the tracking and wait_serialising_requests().