A reliable port cross-build failure (hangup) in my context (amd64->armv7 cross build, with native-tool speedup involved) [details of a specific qemu-arm-static source code problem]

[Mark Millard]

On 2018-Dec-30, at 21:01, Jonathan Chen <jonc at chen.org.nz> wrote:

> On Mon, 31 Dec 2018 at 14:34, Mark Millard via freebsd-ports
> <freebsd-ports at freebsd.org> wrote:
>> 
>> [Removing __packed did make the size and offsets match armv7
>> and the build worked based on the reconstructed qemu-arm-static.]
> 
> Thanks for the analysis Mark! I've been suffering quite a few hangups
> with my ports crossbuilds on amd64->armv7 on 12-STABLE, and I'll be
> trying your suggestions to see whether it resolves the issue.

If you have something like a kqread state for a hang-up consistently
in the same place, then Mikael Urankar 's fix (or any other
way of getting the right sizes and field offsets for kevent) has a
chance of fixing what you have observed.

But if you have a form of hang-up that shows no sign of being tied
to kevent or hangs-up only sometimes, I'd be surprised if the __packed
change(s) would fix the issue.

I've seen such racy hang-ups from lld's creation of (#cpu)+2 threads,
as FreeBSD counts cpus. I've selectively forced -Wl,--no-threads at
times in specific contexts to avoid that. binutils ld does not tolerate
the option. ports does not appear to have an equivalent of:

LDFLAGS.lld+= -Wl,--no-threads

that would be lld specific.


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)