Re: [Qemu-devel] [PATCH v6 00/12] cpu-exec: Safe work in quiescent state

[Paolo Bonzini]

On 05/09/2016 17:51, Alex Bennée wrote:
> And then ran the test in my pigz testing image:
> 
>     ./tests/docker/docker.py update pigz-test:armhf ./arm-linux-user/qemu-arm
>     retry.py -n 20 -c -- docker run -i -t --rm pigz-test:armhf pigz data.tar
> 
> An observed the results of flushing including racing flushes which would
> ordinarily take out the system.
> 
> It would be nice to resurrect some of the tests/tcg stuff and see if we
> can stress linux-user with creating and destroying threads. I guess the
> work here also replaces Emilo's RCU cpu list.

Sort of, uses of CPU_FOREACH should be protected by RCU which isn't yet
the case.  But yes, that was the idea behind using a single mutex.

Related to this, in fact you don't need to hold the mutex between
start_exclusive and end_exclusive.  You can release it at the end of
start_exclusive and take it again for end_exclusive.  That's a bit nicer
to reason about without making the mutex recursive mutexes.

Paolo