[DOC] Doc for Thread::ConditionVariable #13024
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peterzhu2118
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Documented the necessity of calling `wait` in a loop. We modified the example to demonstrate the idiomatic use, and added a third thread `a2` to demonstrate another reason that necessitates the loop. Mentioned spurious wake-up in the doc.
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@peterzhu2118 I have re-written part of the example and added a third thread |
peterzhu2118
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Apr 2, 2025
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Documented the necessity of calling
waitin a loop. We modified theexample and added a third thread
a2to make the point clearer.Mentioned spurious wake-up in the doc.
The example in the documentation of
Thread::ConditionVariableis wrong. Condition variables should use a separate boolean predicate, and should be waited in a loop due to nondeterministic scheduling and spurious wake-ups. This pull request explains these issues and provides the right example. FYI, the documentation of other programming languages or libraries (such as POSIX thread, C++, Java, Rust and Python) also describe such issues and provide relevant examples.The current documentation does not mention whether spurious wake-ups are allowed, but from the function name
rb_thread_sleep_deadly_allow_spurious_wakeupand the invocation ofsleep_hrtime(..., 0), it is apparent that spurious wake-ups are possible. This pull request documented this, too. The presence of spurious wake-ups does not affect the use of condition variables because they always need to be waited in a loop anyway.