# std::atomic_flag::notify_all

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< cpp‎ | atomic‎ | atomic flag

|  | (since C++20)
void notify_all() noexcept; |  |
void notify_all() volatile noexcept; |  |

Performs atomic notifying operations.

Unblocks all threads blocked in atomic waiting operations (i.e. wait()) on *this, if there are any; otherwise does nothing.

### Return value

(none)

### Notes

This form of change-detection is often more efficient than simple polling or pure spinlocks.

### Example

| This section is incomplete Reason: no example

### See also

wait (C++20) | blocks the thread until notified and the atomic value changes (public member function)
atomic_flag_wait atomic_flag_wait_explicit (C++20)(C++20) | blocks the thread until notified and the flag changes (function)
atomic_flag_notify_one (C++20) | notifies a thread blocked in atomic_flag_wait (function)

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