I sure wish they'd rewrite the Azure Linux VM Agent in Rust. That thing normally burns 10-15% of a core, and also blocks VM restart for tens of minutes, god knows why.

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loeg 3 hours ago | parent | next [-]

I've seen certain MSFT engineers get a lock ordering warning from taking mutexes in a wrong order and "fix" it by using a spin loop + try lock instead.

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senderista 2 hours ago | parent [-]

I work on a commercial database marketed as "lock-free" and I can't tell you how many CAS spin loops I've seen with no backoff or iteration bounds.

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cowlevel 14 minutes ago | parent | next [-]

If it only retries because a different thread made progress, it's lock-free and total work is bounded - even though one particular thread could get very unlucky, system-wide luck is conserved.

How much code's inside the CAS loop? If it's being held for less than (sticks finger in the wind) a few thousand of instructions then backoff or limits are actively counterproductive. That's how you're supposed to use a CAS loop.

If it's more, you shouldn't try to invent a more clever CAS loop, you should replace it with a mutex.

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masklinn an hour ago | parent | prev [-]

Does the system provide ready made backoff and / or bounded CAS loop primitives? Because if you have to write the entire thing in full every time I can see why it’s get skipped.

	▲	cowlevel 12 minutes ago \| parent [-]
		Normally if you find yourself needing something like that, it means a CAS loop is the wrong tool for the job.

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arccy an hour ago | parent | prev [-]

no amount of rust will fix the problems in azure that lead to https://news.ycombinator.com/item?id=47616242