std:: atomic_flag_wait, std:: atomic_flag_wait_explicit
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Defined in header
<atomic>
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void
atomic_flag_wait
(
const
atomic_flag
*
object,
bool
old
)
noexcept
;
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(1) | (since C++20) |
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void
atomic_flag_wait
(
const
volatile
atomic_flag
*
object,
bool old ) noexcept ; |
(2) | (since C++20) |
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void
atomic_flag_wait_explicit
(
const
atomic_flag
*
object,
bool old, std:: memory_order order ) noexcept ; |
(3) | (since C++20) |
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void
atomic_flag_wait_explicit
(
const
volatile
atomic_flag
*
object,
bool old, std:: memory_order order ) noexcept ; |
(4) | (since C++20) |
Performs atomic waiting operations.
Compares object - > test ( std:: memory_order_seq_cst ) or object - > test ( order ) with old , and if they are equal then blocks until * object is notified by std::atomic_flag::notify_one() or std::atomic_flag::notify_all() (or the thread is unblocked spuriously). This is repeated until the values compare unequal.
These functions are guaranteed to return only if value has changed, even if underlying implementation unblocks spuriously.
Parameters
| object | - | pointer to the atomic flag to check and wait on |
| old | - | the value to check the atomic flag no longer contains |
| order | - | the memory synchronization ordering |
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.
Example
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This section is incomplete
Reason: no example |
See also
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(C++20)
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notifies at least one thread waiting on the atomic object
(public member function of
std::atomic_flag
)
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(C++20)
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notifies all threads blocked waiting on the atomic object
(public member function of
std::atomic_flag
)
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(C++20)
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notifies a thread blocked in atomic_flag_wait
(function) |
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(C++20)
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notifies all threads blocked in atomic_flag_wait
(function) |