33 Thread support library [thread]

33.5 Condition variables [thread.condition]

33.5.2 Non-member functions [thread.condition.nonmember]

void notify_all_at_thread_exit(condition_variable& cond, unique_lock<mutex> lk);
Requires: lk is locked by the calling thread and either
  • no other thread is waiting on cond, or
  • lk.mutex() returns the same value for each of the lock arguments supplied by all concurrently waiting (via wait, wait_­for, or wait_­until) threads.
Effects: Transfers ownership of the lock associated with lk into internal storage and schedules cond to be notified when the current thread exits, after all objects of thread storage duration associated with the current thread have been destroyed.
This notification shall be as if:
lk.unlock();
cond.notify_all();
Synchronization: The implied lk.unlock() call is sequenced after the destruction of all objects with thread storage duration associated with the current thread.
[Note
:
The supplied lock will be held until the thread exits, and care should be taken to ensure that this does not cause deadlock due to lock ordering issues.
After calling notify_­all_­at_­thread_­exit it is recommended that the thread should be exited as soon as possible, and that no blocking or time-consuming tasks are run on that thread.
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]
[Note
:
It is the user's responsibility to ensure that waiting threads do not erroneously assume that the thread has finished if they experience spurious wakeups.
This typically requires that the condition being waited for is satisfied while holding the lock on lk, and that this lock is not released and reacquired prior to calling notify_­all_­at_­thread_­exit.
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]