Re: [Qemu-devel] [RFC PATCH V3 0/3] Multithread TCG async_safe_work part.

[Frederic Konrad]

On 20/07/2015 19:36, Alex Bennée wrote:
> address@hidden writes:
>
> > From: KONRAD Frederic <address@hidden>
> >
> > This is the async_safe_work introduction bit of the Multithread TCG work.
> > Rebased on current upstream (6169b60285fe1ff730d840a49527e721bfb30899).
> >
> > (Currently untested as I need to rebase MTTCG first.)
> >
> > It can be cloned here:
> > http://git.greensocs.com/fkonrad/mttcg.git branch async_work_v3
> >
> > The first patch introduces a mutex to protect the existing queued_work_*
> > CPUState members against multiple (concurent) access.
> >
> > The second patch introduces a tcg_exec_flag which will be 1 when we are inside
> > cpu_exec(), -1 when we must not enter the cpu execution and 0 when we are
> > allowed to do so. This is required as safe work need to be sure that's all vCPU
> > are outside cpu_exec().
> >
> > The last patch introduces async_safe_work. It allows to add some work which will
> > be done asynchronously but only when all vCPUs are outside cpu_exec(). The tcg
> > thread will wait that no vCPUs have any pending safe work before reentering
> > cpu-exec().
> >
> > Changes V2 -> V3:
> >    * Check atomically we are not in the executiong loop to fix the race 
> > condition
> >      which might happen.
> > Changes V1 -> V2:
> >    * Release the lock while running the callback for both async and safe work.
> >
> > KONRAD Frederic (3):
> >    cpus: protect queued_work_* with work_mutex.
> >    cpus: add tcg_exec_flag.
> >    cpus: introduce async_run_safe_work_on_cpu.
> Also currently breaks a lot of targets:
>
> https://travis-ci.org/stsquad/qemu/builds/71797143

oops yes, seems linux-user is not happy at all.
Will fix that.

Thanks,
Fred
> >   cpu-exec.c        |  10 ++++
> >   cpus.c            | 160 ++++++++++++++++++++++++++++++++++++++++--------------
> >   include/qom/cpu.h |  57 +++++++++++++++++++
> >   qom/cpu.c         |  20 +++++++
> >   4 files changed, 207 insertions(+), 40 deletions(-)