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Why is my CPU usage always 100%?

If you’re new to this series, I’ve been documenting the process I went through upgrading my old PXA166-based Chumby 8’s 2.6.28 Linux kernel to a modern 6.x version. Here are links to parts 1, 2, 3, 4, 5, 6, 7, and 8.

I focused on /proc/stat, which is responsible for providing the info in the second line of top’s output showing how the CPU load is distributed between user, system, idle, etc. Around this point, I remembered that Chumby’s original 2.6.28 kernel worked correctly, so I decided to take a look at its version of this section of code. The second link seemed to just ignore the risk of metastability altogether when in 32.768 KHz mode, and otherwise also implemented a solution similar to the old Chumby kernel.

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