Help figure out why make freezes - no errors or messages

For Developers
1

I am setting up my windows 11 tablet, Surface 10 Pro, to compile openwrt for my Mikrotik RB493G router. I don't have any other computers to install Linux on; they are all dead for various reasons. Netboot has a 4MB kernel limit and the openwrt initramfs is currently about 7MB. I plan to compile a copy of the openwrt release 24.10.2 to make sure I have a good environment before I start removing things like IPv6 to shrink the initramfs. I don't need IPv6 to netboot. I have followed the directions and I am at the part where I compile the kernel. I run make and it freezes after:
make[3] -C tools/llvm-bpf clean-build
make[3] -C tools/llvm-bpf compile

There is nothing else. It just sits there for hours, 3 to 4 hours. I ran make distclean and tried a second time but it freezes at the same spot. I tried another make distclean and ran make V=s 2>&1 | tee build.log | grep -i -E "^make.*(error|[12345]...Entering dir)" but that didn't give me any more information. How can I figure out what am I doing wrong?

These are steps I have followed to get to this point:

cmd - run as administrator
wsl --install -d Debian
sudo apt update
sudo apt dist-upgrade
sudo tee -a /etc/wsl.conf << EOF > /dev/null
[interop]
appendWindowsPath = false
EOF
exit
wsl --shutdown
wsl -d Debian

sudo apt install build-essential clang flex bison g++ gawk \
gcc-multilib g++-multilib gettext git libncurses5-dev libssl-dev \
python3-setuptools rsync swig unzip zlib1g-dev file wget

git clone https://git.openwrt.org/openwrt/openwrt.git
cd openwrt
git pull 

git checkout v24.10.2
./scripts/feeds update -a
./scripts/feeds install -a

wget https://downloads.openwrt.org/releases/24.10.2/targets/ath79/mikrotik/config.buildinfo -O .config
make menuconfig
select rb493g for target profile, save, and quit

make download
make
2

What's the CPU in that thing ?

Have you checked the CPU load while compiling, in a parallel window/session?

3

14 Intel Ultra 7165U processors
Yes. When it is compiling the first part CPU usage varies between 10-25%. After the compiler gets to
make[3] -C tools/llvm-bpf clean-build
make[3] -C tools/llvm-bpf compile
CPU usage drops to 0.

4

Compile with make V=sc to get the full output and see where it hangs.

5

This time it compiled fine. Diff and sha256sum show differences between my initramfs and openwrts. Is it possible to generate the exact same file that is downloadable from openwrt?

6

It probably runs out of memory and becomes unresponsive.

  • You can try using less threads for the making, e.g if you are doing make -j8 try make -j4
  • If the system just doesn't have enough memory you can try making a zram swap, or use a hard drive via usb as swap.
  • Or you can make sure your host has nbd support and then use nbdkit on another machine to share it's memory over. e.g..
on remote machine:
nbdkit -p 3000 memory allocator=zstd  20G
on build host:
modprobe nbd
nbd-client [ip of remote machine] 3000
mkswap /dev/nbd0
swapon -d /dev/nbd0
7

make fails
make -j1 V=sc works

I would think 16GB is enough, but it is windows compiling a Linux kernel, so you are probably right. I need to one of my Linux boxes repaired.

8

Hmm, yeah not sure, maybe there is an environment variable setting the MAKEFLAGS=jX to a number too large for the amount of ram the system has /shrug

9

24GB RAM VMs using some half crappy ARM CPUs are still free for life over at Oracle Cloud.

Create one, compile there.
But I have to admit, I haven't tried doing it on ARM, only x86.

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