Sorry about this, this was a brain-freeze case.
I was made to realize that it is the wait_at_barrier field initialized
to 1 and not workers_at_barrier
Once again sorry for spamming on this one. Everything's fine here.
Regards
-Prashant
On Tue, Nov 13, 2018 at 5:50 PM Prashant Upadhyaya
<praupadhy...@gmail.com> wrote:
>
> Hi,
>
> I am on VPP 18.01.
>
> I see the following while loop in the
> vlib_worker_thread_barrier_sync_int function
> (src/vlib/threads.c)
> while (*vlib_worker_threads->workers_at_barrier != count)
> {
> if ((now = vlib_time_now (vm)) > deadline)
> {
> fformat (stderr, "%s: worker thread deadlock\n", __FUNCTION__);
> os_panic ();
> }
> }
> Suppose I have 4 workers (and 1 main thread), so the value of count will be 4.
> Each worker bumps up the workers_at_barrier by 1.
> So if the while loop in its sampling misses seeing the value bumping
> by the third worker, and the 4th worker bumps up the value, then
> workers_at_barrier will become 5 and the while will never break
> eventually missing the deadline.
>
> I am seeing this happening occasionally on some of my setups.
>
> Do you think it is safe to change the while like this instead ?
>
> while (*vlib_worker_threads->workers_at_barrier <= count)
>
> Regards
> -Prashant
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