Folding Forum

Subject: FahCore_a8 v0.0.12 segfault on Ubuntu 24.04 LTS / Kernel 6.14 - CPU work units crash immediately
System Information:

OS: Ubuntu 24.04 LTS
Kernel: 6.14
CPU: AMD Ryzen 9 5900X 12-Core Processor (24 threads)
GPU: NVIDIA GeForce RTX 5070 Ti
RAM: 62.72 GiB
F@H Client: v8.4.9
Username: Hemlok
Team: 250299

Problem Description:
All CPU work units fail immediately after starting with "Core was killed" / "Core crashed with exit code 0" errors. GPU folding works perfectly without issues.
Symptoms:

CPU work units (using FahCore_a8 v0.0.12, Gromacs core) consistently crash within seconds of starting
Work units complete only "1 out of 2500000 steps (0%)" before crashing
GPU work units (using Core22, OpenMM) complete successfully
Pattern repeats with every CPU work unit assigned

Example from F@H logs:
20:55:43:I1:WU185:Project: 16959 (Run 19, Clone 116, Gen 991)
20:55:43:I1:WU185:Calling: mdrun -c frame991.gro -s frame991.tpr -x frame991.xtc -cpt 5 -nt 12 -ntmpi 1
20:55:43:I1:WU185:Steps: first=-1817467296 total=-1814967296
20:55:44:I1:WU185:Completed 1 out of 2500000 steps (0%)
20:56:51:E :WU185:Core was killed
20:56:51:E :WU185:Core crashed with exit code 0
20:56:51:E :WU185:Core returned FAILED_1 (0)
20:56:51:E :WU185:Run did not produce any results. Dumping WU
```

**Note:** The negative step numbers (`first=-1817467296 total=-1814967296`) appear unusual and may indicate a corrupted work unit or core issue.

**Kernel logs (dmesg) show segmentation faults:**
```
[15374.949026] FahCore_a8[13727]: segfault at fffffffe2e338230 ip 000000000071b329 sp 000076475dffad70 error 5 in FahCore_a8[31b329,406000+e6d000] likely on CPU 15 (core 3, socket 0)
[15374.949036] Code: 6a 59 d1 c4 41 7a 2c cd c5 7a 2c c1 c5 fa 2c fa c4 c1 7a 2a c1 4d 63 d1 4c 8b 4c 24 30 c4 41 0a 2a f0 c5 12 5c e0 c5 f8 57 c0 <c4> 01 1a 58 2c 91 4d 63 c8 c5 fa 2a c7 4c 8b 44 24 38 c4 41 72 5c

[15493.242565] FahCore_a8[14043]: segfault at fffffffe17b866b0 ip 000000000071b329 sp 000072e7f6ffcd70 error 5 in FahCore_a8[31b329,406000+e6d000] likely on CPU 20 (core 10, socket 0)
[15493.242579] Code: 6a 59 d1 c4 41 7a 2c cd c5 7a 2c c1 c5 fa 2c fa c4 c1 7a 2a c1 4d 63 d1 4c 8b 4c 24 30 c4 41 0a 2a f0 c5 12 5c e0 c5 f8 57 c0 <c4> 01 1a 58 2c 91 4d 63 c8 c5 fa 2a c7 4c 8b 44 24 38 c4 41 72 5c
```

**FahCore_a8 details:**
```
Core: Gromacs
Type: 0xa8
Version: 0.0.12
Date: Jan 16 2021
Time: 19:24:44
Compiler: GNU 8.3.0
Platform: linux2 4.15.0-128-generic
Bits: 64
Mode: Release
SIMD: avx2_256
OpenMP: ON
CUDA: OFF
Root Cause:
The FahCore_a8 binary (compiled for kernel 4.15.0-128) is experiencing memory access violations (segfaults) when running on the modern kernel 6.14. The core is attempting to access invalid memory addresses, causing immediate crashes.
Troubleshooting steps attempted:

Fixed v7 to v8 config file migration issues (removed deprecated options: gpu, fold-anon, pci-bus, pci-slot)
Deleted and re-downloaded FahCore_a8 (rm -rf /var/lib/fah-client/cores/fahcore-a8*)
Full service restart
Tried multiple different CPU work units - all crash with identical symptoms
Verified no DNS/network issues (other computers on network fold successfully, GPU folding works)
Checked dmesg logs - confirmed segmentation faults in FahCore_a8

Workaround:
Currently running with CPU folding disabled (<cpus value="0"/> in config.xml). GPU folding continues to work flawlessly.
Question:
Is there a newer version of FahCore_a8 available that's compatible with Ubuntu 24.04 / kernel 6.14? Or is this a known issue with a planned fix?
The core appears to be nearly 4 years old (Jan 2021) and may need to be recompiled for modern Linux kernels.

There is nothing wrong with the core. Your CPU/system is unstable

Run full system stability test, like y-cruncher for extensive amount of time to determine if the system is stable or not. The way yours craps out straight away, it might be temperature of the cpu

How can I test this suggestion further? I stress tested each section of this recently assembled computer one at a time. This is an open case system with air cooling, and it settles in at 70deg C at 100% load. Isn't that well under what this CPU should be capable of? I've been folding on many machines over many years but this is the first time that I've seen this. If I have a flakey CPU, I'm nor sure how to confirm. I used AI to walk me through one test at time for each major component, but I don't have another MB to swap to and have not had time to swap the PSU. That said, this is a top brand 1200w so I'm not expeting that to be a factor when the folding fails on the first unit every time.

mark@titan:~$ stress-ng --cpu 0 --timeout 15m --metrics-brief
stress-ng: info: [14383] setting to a 15 mins, 0 secs run per stressor
stress-ng: info: [14383] dispatching hogs: 24 cpu
stress-ng: info: [14383] note: 24 cpus have scaling governors set to powersave and this can impact on performance; setting /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor to 'performance' may improve performance
stress-ng: metrc: [14383] stressor bogo ops real time usr time sys time bogo ops/s bogo ops/s
stress-ng: metrc: [14383] (secs) (secs) (secs) (real time) (usr+sys time)
stress-ng: metrc: [14383] cpu 32984624 900.00 21320.83 13.10 36649.54 1546.11
stress-ng: info: [14383] skipped: 0
stress-ng: info: [14383] passed: 24: cpu (24)
stress-ng: info: [14383] failed: 0
stress-ng: info: [14383] metrics untrustworthy: 0
stress-ng: info: [14383] successful run completed in 15 mins, 0.01 secs

## Diagnostic Summary & Final Steps
We have now tested every major component that can be reliably checked with software, and they have all passed with flying colors.
-Memory (RAM): Passed
-Graphics Card (GPU): Passed
-Processor (CPU) & Cooling: Passed
-Storage (NVMe SSD): Passed

When the CPU, RAM, GPU, and storage all test clean, suspicion falls on the two components that are very difficult to test with software: the Power Supply Unit (PSU) and the Motherboard.

run y-cruncher, which loads your system fully

Does it happen with all WUs or only with this one ?