Hi,

After I got the 4.19 Liquorix kernel I have had problems with suspend on my Thinkpad T460S running Ubuntu 18.10. After it has been running for a while it will not suspend when I close the lid and it has caused a very hot laptop in my backpack! :)

It does suspend normally right after boot, but after a couple of hours it doesn't even if I push the power button. I have to fully shut down. I would assume this is hard to troubleshoot so I will stick to stock kernel for now and try when there's a new Liqourix release. If there's a fix for this that would be best of course so I can come back on Liquorix.
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Specific kernels often have issues that break suspend, on my thinkpads, over the years, I adopt the simple but effective strategy when this happens to always keep 2 kernels that are known good installed, then to install the latest, and if I hit suspend issues, remove the latest, and wait until the issue is fixed. Because thinkpads are pretty popular among kernel developers, such issues tend to get resolved over time more often than not.

This is a general strategy, when it comes to specific kernels, there may be specific issues, but I found over the years it was a waste of time trying to track them down since the suspend usually returns to functionality eventually, and if you're honest, a new kernel rarely does anything you need that badly if the old kernel worked fine.

If you want to be more proactive, make sure to file issue reports upstream after confirming that vanilla kernels also have this issue. If it turns out that it's a liquorix specific issue, then it could be some new configuration damentz is trying, so you'd want to let him know it's liquorix specific, but always verify on a known standard kernel like Debian, or Ubuntu in your case, I assume there's a PPA or something with recent kernels for ubuntu?, that way you can file an issue against it that might go upstream and do some good.
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The only thing I can suggest is try disabling transparent hugepages with transparent_hugepage=never in your kernel parameters. They're on by default now on Liquorix with defer+madvise as the default defrag/compaction strategy since this provides a decent balance between higher throughput with a fast fallback to regular pages when external fragmentation is high. Compaction happens later without blocking applications, thus the defer defrag strategy.

However, on one occasion after enabling it with some custom aggressive khugepaged settings, I did experience a freeze on an attempt to suspend. After removing those custom settings I couldn't reproduce it, so I chalked it up running khugepaged with insane settings.

Let me know if that helps.
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Thanks! Good advice and suggestion. I will try to kernel parameter since it's an easy (potential) fix. Otherwise, as I said I assumed it would be beyond my capabilities to troubleshoot this, so kept stock kernel in addition to a 4.18 Liqorix kernel, so I'm good for now. I
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As luck would have it, I think I found what's causing suspend to break on specific hardware configurations. A patch was added many stable patches ago on 4.19 that breaks suspend with laptops utilizing USB in weird ways internally.

Here's the commit that fixes it: github.com/zen-kernel/zen-kernel/commit/a4ce1e8cf

The AUR and Debian kernels are fixed. I forgot to clean up my Ubuntu PPA so they're just now building after I resubmitted the package sources, but they everything should be published in 4 hours.

Crossing my fingers, let me know if this helps.
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