Fix a race in thread wakeup #459
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ghost
commented
Jun 29, 2018
| /// use std::time::Duration; | ||
| /// | ||
| /// # pub fn main() { | ||
| /// // Create a thread pool with default configuration values |
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I found this comment confusing. It seems to imply that the example shows how the builder is configured by default. However, this comment applies only to Builder::new(), while the chained methods do custom configuration (which is different from default).
Perhaps a different sentence would work better, but due to lack of ideas I've decided to simply remove it. :)
carllerche
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Jul 3, 2018
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carllerche
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Good eye! That is definitely an issue.
| /// use std::time::Duration; | ||
| /// | ||
| /// # pub fn main() { | ||
| /// // Create a thread pool with default configuration values |
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This was referenced Aug 6, 2018
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When unparking a worker thread, we do the following steps:
The problem occurs if the thread transitions from SLEEP to IDLE between steps 1 and 2. In that case, step 3 will fail to transition and simply return from
unpark.This PR changes the step 3 so that we always transition to NOTIFY, no matter what the previous state was.
The park/unpark mechanism in
std::threadworks somewhat similarly. In step 3, it attempts to CAS from SLEEP to NOTIFY, but jumps back to step 1 if the previous state was IDLE. See here. I've decided to unconditionally move to state NOTIFY instead - the end result should be the same.In addition to that, I did a bunch of random improvements to the documentation.