std::condition_variable::wait (3) - Linux Man Pages
void wait( std::unique_lock<std::mutex>& lock ); (1) (since C++11)
template< class Predicate > (2) (since C++11)
void wait( std::unique_lock<std::mutex>& lock, Predicate pred );
wait causes the current thread to block until the condition variable is notified or a spurious wakeup occurs, optionally looping until some predicate is satisfied.
1) Atomically unlocks lock, blocks the current executing thread, and adds it to the list of threads waiting on *this. The thread will be unblocked when notify_all() or notify_one() is executed. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait exits.
If this function exits via exception, lock is also reacquired.
2) Equivalent to
This overload may be used to ignore spurious awakenings while waiting for a specific condition to become true.
Note that lock must be acquired before entering this method, and it is reacquired after wait(lock) exits, which means that lock can be used to guard access to pred().
If these functions fail to meet the postconditions (lock.owns_lock()==true and lock.mutex() is locked by the calling thread), std::terminate is called. For example, this could happen if relocking the mutex throws an exception, (since C++14)
lock - an object of type std::unique_lock<std::mutex>, which must be locked by the current thread
pred - The signature of the predicate function should be equivalent to the following:
May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock(). (until C++14)
Does not throw (since C++14)
2) Same as (1) but may also propagate exceptions thrown by pred
Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
Calling this function if lock.mutex() is not the same mutex as the one used by all other threads that are currently waiting on the same condition variable is undefined behavior.
The effects of notify_one()/notify_all() and each of the three atomic parts of wait()/wait_for()/wait_until() (unlock+wait, wakeup, and lock) take place in a single total order that can be viewed as modification_order of an atomic variable: the order is specific to this individual condition_variable. This makes it impossible for notify_one() to, for example, be delayed and unblock a thread that started waiting just after the call to notify_one() was made.
// Run this code
wait_for (public member function)