Difference between revisions of "cpp/atomic/atomic wait"
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===Example=== | ===Example=== | ||
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===See also=== | ===See also=== | ||
Revision as of 07:57, 8 February 2020
| Defined in header <atomic>
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| (1) | (since C++20) | |
| template< class T > void atomic_wait( const std::atomic<T>* object, |
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| template< class T > void atomic_wait( const volatile std::atomic<T>* object, |
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| (2) | (since C++20) | |
| template< class T > void atomic_wait_explicit( const std::atomic<T>* object, |
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| template< class T > void atomic_wait_explicit( const volatile std::atomic<T>* object, |
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Performs atomic waiting operations.
Compares the value representation of the object->load(std::memory_order_seq_cst) or object->load(order) with that of old, and if those are bitwise equal then blocks until the one of result of loading changes or *object is notified by std::atomic::notify_one() or std::atomic::notify_one().
These functions are allowed to unblock spuriously, i.e. return due to reasons other than value change or notification.
Contents |
Parameters
| object | - | pointer to the atomic object to check and wait on |
| old | - | the value to check the atomic object no longer contains |
| order | - | the memory synchronization ordering for this operation: must not be std::memory_order::release or std::memory_order::acq_rel |
Return value
(none)
Notes
This form of change-detection is often more efficient than simple polling or pure spinlocks.
Due to the ABA problem, transient changes from old to another value and back to old might be missed, and not unblock.
The comparison is bitwise (similar to std::memcpy); no comparison operator is used. Padding bits that never participate in an object's value representation are ignored.
Example
| This section is incomplete Reason: no example |
See also
| (C++20) |
notifies at least one thread waiting on the atomic object (public member function of std::atomic<T>)
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| (C++20) |
notifies all threads blocked waiting on the atomic object (public member function of std::atomic<T>)
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| (C++20) |
notifies a thread blocked in atomic_wait (function template) |
| (C++20) |
notifies all threads blocked in atomic_wait (function template) |
