[jira] [Resolved] (IMPALA-6125) Fix the usage patterns of condition variables

["Zoltán Borók-Nagy (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-6125?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zoltán Borók-Nagy resolved IMPALA-6125.
---------------------------------------
    Resolution: Fixed

> Fix the usage patterns of condition variables
> ---------------------------------------------
>
>                 Key: IMPALA-6125
>                 URL: https://issues.apache.org/jira/browse/IMPALA-6125
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Zoltán Borók-Nagy
>            Assignee: Zoltán Borók-Nagy
>            Priority: Minor
>
> We should keep ourselves to the following good practices when using a condition variable:
> * favor notify_one over notify_all
> * the mutex associated with a condition variable should have been released by the time calling notify_* on the condition variable
> * favor impala::ConditionVariable over boost::condition_variable
> There are exceptions to all of these rules:
> Use notify_all when:
> * Different threads waiting on different condition expressions
> * The operations of the waiting threads differ
> * Multiple threads are needed to do the job
> Hold mutex during notify:
> * when the call of notify_*() is in the middle of a complex critical section. Still, my guess is most of the time the code can be restructured to release the lock before calling notify.
> * if there can be ownership issues, like in util/promise.h
> boost::condition_variable:
> * the boost thread library supports thread interruption, impala::ConditionVariable doesn't (this is why it has lower overhead). If you need thread interruption, use boost::condition_variable



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