Help needed: Weird bootstrapping hangs

[Ekaitz Zarraga <ekaitz@elenq.tech>]

Hi all,

Really weird question here. Beware.

I'm experiencing weird Guix hangs in the bootstrapping packages.

They happen randomly but frequently in:

- Mes' configure script
- Mes' linking of libtcc
- Some other packages' configure scripts (I had it in Binutils but the 
package is not published yet)
- When creating a Makefile or a config.log in several packages. Even 
after an error appears, they don't stop, they just hang.

The symptoms are the following:

- The stdout of the configure script is just frozen.
- The CPU usage drops, that specific process goes to exactly 20% of CPU 
as seen in `htop`.
- If I connect to the running program using strace I see the following 
forever, appearing very fast in the screen:

pselect6(4, [3], NULL, NULL, {tv_sec=0, tv_nsec=160000}, NULL) = 0 (Timeout)
wait4(14338, 0x7fffffffc5a0, WNOHANG, NULL) = 0
pselect6(4, [3], NULL, NULL, {tv_sec=0, tv_nsec=160000}, NULL) = 0 (Timeout)
wait4(14338, 0x7fffffffc5a0, WNOHANG, NULL) = 0
pselect6(4, [3], NULL, NULL, {tv_sec=0, tv_nsec=160000}, NULL) = 0 (Timeout)
wait4(14338, 0x7fffffffc5a0, WNOHANG, NULL) = 0
pselect6(4, [3], NULL, NULL, {tv_sec=0, tv_nsec=160000}, NULL) = 0 (Timeout)
wait4(14338, 0x7fffffffc5a0, WNOHANG, NULL) = 0

I've replicated this in a separate RISC-V machine so it's not Qemu.

Does anyone have an idea of what can this be?

We have two suspects:
- Guix
- Gash

I have no idea of how to dig on this further. Yesterday I had the same 
hang in both machines' Mes configure scripts but then I added -x to the 
`set -e` on the top of the file and both worked, and they keep working 
since. Then one of them exploded later... I went to bed and I woke up 
with a "Process unresponsive after 3600 seconds" error and I run it 
again and it worked and managed to finish.

Some help would be much appreciated.

Thanks,
Ekaitz