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Comment by AnimalMuppet | Hacker News Reader

What you say is true, but (as far as I can tell) unrelated to the issue at hand. Yes, if you return holding a lock, it's a potential disaster. And if you pause a thread from outside while the thread is holding a lock, it's a similar disaster. But RAII and scoped_lock won't save you if a thread is paused from outside, since the paused thread never makes it out of the scope that took the lock.

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You are talking about some theoretical thing that doesn't apply here. There is no facility in std::jthread that allows it to become "paused".

Then what was lrossi referring to when he (?) said:

>>> The ability to pause a thread from outside is interesting, but it doesn’t seem very useful in general.

>>> It also comes with risks. What if it’s holding a lock? That could cause a performance/latency disaster.

Which you replied to, not claiming that it couldn't be paused from outside, but instead that the lock risk was just the same as returning from a function.

It's difficult to get the point across on the Internet, but lrossi's statement is just nonsense. std::jthread has not introduced any new risks with respect to locking.

You are right, the sleep functions apply only to “this_thread”. What confused me is the comment for the two functions, which refer to the thread as “t” and not “this_thread”; which also matches the naming used for the “is_joinable” function, where it is not the current thread.

So I thought it’s a way to do back pressure across threads, which could be useful, but I was clearly wrong. My bad, but also not a great choice of naming things in the original article.

Then again, if you can only put the current thread to sleep, why have a function for it? Why not call sleep directly?

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