Re: [PATCH 0/5] migration/multifd: Fix channel creation vs. cleanup races

[Peter Xu <peterx@redhat.com>]

On Fri, Feb 02, 2024 at 04:11:23PM -0300, Fabiano Rosas wrote:
> Hi,
> 
> This contains 2 patches from my previous series addressing the
> p->running misuse and the TLS thread leak and 3 new patches to fix the
> cleanup-while-creating-threads race.
> 
> For the p->running I'm keeping the idea from the other series to
> remove p->running and use a more narrow p->thread_created flag. This
> flag is used only inform whether the thread has been created so we can
> join it.
> 
> For the cleanup race I have moved some code around and added a
> semaphore to make multifd_save_setup() only return once all channel
> creation tasks have started.
> 
> The idea is that after multifd_save_setup() returns, no new creations
> are in flight and the p->thread_created flags will never change again,
> so they're enough to cause the cleanup code to wait for the threads to
> join.
> 
> CI run: https://gitlab.com/farosas/qemu/-/pipelines/1162798843
> 
> @Peter: I can rebase this on top of your series once we decide about
> it.

I have one thing to double check with you in patch 5, besides that the
whole set looks all good to me.  Copy Dan here in case he has any input.

If you confirm both sides (my replies to last patch of both this set and
the other lockless change of mine), feel free to repost directly based on
that series for v2.

Thanks,

-- 
Peter Xu