rare gmake jobserver hangs, lost SIGCHLD?

[Don Lewis]

On 13 Feb, Rodney W. Grimes wrote:
>> On Tue, Feb 13, 2018 at 10:46:32AM -0800, Don Lewis wrote:
>> > Starting in December 2016, I've seen three build runaway failures on
>> > different ports.
>> 
>> https://savannah.gnu.org/bugs/?49014 might be your problem.
> 
> And given you said Ryzen earlier there is also this issue just found
> and fixed:
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=225584

Yes, I tested that patch and found that it got rid of several different
semi-random port build failures.  I just happened to get this
gmake-related build runaway on my first poudriere run after applying the
VM patch.