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@Louson Never forget: It is easier to circle the square than to square the circle.
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@jwseigh Rightly or wrongly, this site says tau is 2π. https://en.wikipedia.org/wiki/Tau_(mathematics)

Me, I glanced too quickly at the first occurrence of 𝜏 (tau) in this thread and mistook it for the Roman-alphabet letter "r". ;-)
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@tommythorn Indeed, 2π day and 𝜏 day are one and the same! But I suspect that more people would prefer to eat two pies than would prefer to eat a tau. ;-)
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@morgan I would attempt a witty response, but I would probably end up sounding like a square. ;-)
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Paul E. McKenney

Happy 2π day to those who celebrate it!
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@brauner Fair enough! But I might nor might not remember that you forgot. ;-)
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@brauner RCU uses many mutexes so that RCU users don't have to? ;-)
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@sima @brauner @jann @vbabka RCU is benign? May I please get that in writing? ;-)
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@ljs @jann That does sound like it might require unusually disciplined users! But what is it currently used for?
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@ljs It is amazing how destructive unanticipated use cases can be. Destructive, but necessary...
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@brauner @jann It has been a very long time since I have seen a local filesystem operation take very long, so no argument here!
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@brauner @jann Use AI to find the xfstest of interest? (OK, OK, I will get my coat...)
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@jann @brauner As always, the big question is "what would have detected the bug earlier and more deterministically?" Finding the extreme corner cases is inherently hard, because that is exactly why we call them "extreme".
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@jann @brauner Or to recover from the next timeout being unduly delayed, for that matter. That said, in my experience, most timeout handlers unconditionally do their work. On the other hand, I could easily believe that unconditional timeout handlers are much less likely to come to your attention. ;-)
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@brauner @jann Or a way to fuzz the timers. Though some would argue that the kernel as it is does a pretty good job of this sort of fuzzing...
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@brauner @jann To be fair, that does fall into the first of Jann's valid use cases: "a remote system is not responding, drop the connection and maybe connect again later".
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@brauner @jann Interruptible/killable sleeping locks can be used for latency reduction for the poor user who didn't realize how long things might take.

Of course, there just might a few Interruptible/killable sleep-lock failure paths in need of better testing... ;-)
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@jann Another use case is periodic polling. Yet another is dealing with latency constraints, for example, compute it the hard and accurate way, but if that takes too long, compute it more quickly and less accurately. Another involves needing to do things that are not permitted in a restrictive context (e.g., interrupt handler), though things like irq work are better on architectures providing this.

All that aside, yes, I have seen timeouts used in cases where investing a little more thought might have provided a better solution. Then again, the same is true of pretty much all other facilities provided by the Linux kernel. ;-)
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@jann Timeouts. Can't live with them, can't live without them. ;-)
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Slides from this weekend's Oregon State University Beaver BarCamp. Unusual topic, but a request. Fun session, good interaction.

https://drive.google.com/file/d/1-0si8ZhUTE-SA94g_mrBvJuVL1GoQrZ9/view?usp=sharing
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