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### 1220. What does `condition_variable` wait on?

Section: 33.7 [thread.condition] Status: C++11 Submitter: Jeffrey Yasskin Opened: 2009-09-30 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

"Class `condition_variable` provides a condition variable that can only wait on an object of type `unique_lock`" should say "...object of type `unique_lock<mutex>`"

[ 2009-11-06 Howard adds: ]

> Moved to Tentatively Ready after 5 positive votes on c++std-lib.

Proposed resolution:

Change 33.7 [thread.condition], p1:

> Condition variables provide synchronization primitives used to block a thread until notified by some other thread that some condition is met or until a system time is reached. Class `condition_variable` provides a condition variable that can only wait on an object of type `unique_lock<mutex>`, allowing maximum efficiency on some platforms. Class `condition_variable_any` provides a general condition variable that can wait on objects of user-supplied lock types.