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

[Alex Bennée]

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

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

-- 
Alex Bennée