Difference between revisions of "Template:cpp/atomic/atomic/wait"
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| − | Compares the [[cpp/language/object|value representation]] of the {{c|this->{{#ifeq:{{{1|}}}|atomic_flag|test|load}}(order)}} with that of {{tt|old}}, and if those are bitwise equal then blocks until the one of {{c|this->{{#ifeq:{{{1|}}}|atomic_flag|test|load}}(order)}} changes or {{c|*this}} is notified by {{lc|notify_one()}} or {{lc|notify_all()}}. These functions are allowed to unblock spuriously i.e. return due to reasons other than value change or notification. | + | Compares the [[cpp/language/object|value representation]] of the {{c|this->{{#ifeq:{{{1|}}}|atomic_flag|test|load}}(order)}} with that of {{tt|old}}, and if those are bitwise equal then blocks until the one of {{c|this->{{#ifeq:{{{1|}}}|atomic_flag|test|load}}(order)}} changes or {{c|*this}} is notified by {{lc|notify_one()}} or {{lc|notify_all()}}. These functions are allowed to unblock spuriously, i.e. return due to reasons other than value change or notification. |
This form of change-detection is often more efficient than simple polling or pure spinlocks. | This form of change-detection is often more efficient than simple polling or pure spinlocks. | ||
Revision as of 06:57, 8 February 2020
Template:cpp/atomic//title Template:cpp/atomic//navbar
| (since C++20) | ||
| void wait( T old, std::memory_order = std::memory_order::seq_cst ) const noexcept; |
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| void wait( T old, std::memory_order = std::memory_order::seq_cst ) const volatile noexcept; |
||
Compares the value representation of the this->load(order) with that of old, and if those are bitwise equal then blocks until the one of this->load(order) changes or *this is notified by notify_one() or notify_all(). These functions are allowed to unblock spuriously, i.e. return due to reasons other than value change or notification.
This form of change-detection is often more efficient than simple polling or pure spinlocks.
Contents |
Parameters
| old | - | the value to check the 's 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
Due to the ABA problem, transient changes from old to something else and back to old might be missed, and not unblock.
Example
| This section is incomplete |
See also
| (C++20) |
notifies at least one thread waiting on the atomic object (public member function of Template:cpp/atomic//title)
|
| (C++20) |
notifies all threads blocked waiting on the atomic object (public member function of Template:cpp/atomic//title)
|
| (C++20) |
notifies a thread blocked in atomic_wait (function template) |
| (C++20) |
notifies all threads blocked in atomic_wait (function template) |
