std:: atomic_wait, std:: atomic_wait_explicit
|
Defined in header
<atomic>
|
||
|
template
<
class
T
>
void
atomic_wait
(
const
std::
atomic
<
T
>
*
object,
|
(1) | (since C++20) |
|
template
<
class
T
>
void
atomic_wait
(
const
volatile
std::
atomic
<
T
>
*
object,
|
(2) | (since C++20) |
|
template
<
class
T
>
void
atomic_wait_explicit
(
const
std::
atomic
<
T
>
*
object,
|
(3) | (since C++20) |
|
template
<
class
T
>
void
atomic_wait_explicit
(
const
volatile
std::
atomic
<
T
>
*
object,
|
(4) | (since C++20) |
Performs atomic waiting operations. Behaves as if it repeatedly performs the following steps:
-
Compare the
value representation
of
object
-
>
load
(
)
(for overloads
(1,2)
) or
object
-
>
load
(
order
)
(for overloads
(3,4)
) with that of
old
.
- If those are bitwise equal, then blocks until * object is notified by std::atomic::notify_one() or std::atomic::notify_all() , or the thread is unblocked spuriously.
- Otherwise, returns.
These functions are guaranteed to return only if value has changed, even if the underlying implementation unblocks spuriously.
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 |
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::memcmp ); 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)
|
blocks the thread until notified and the atomic value changes
(public member function of
std::atomic<T>
)
|
|
(C++20)
|
notifies at least one thread waiting on the atomic object
(public member function of
std::atomic<T>
)
|
|
(C++20)
|
notifies all threads blocked waiting on the atomic object
(public member function of
std::atomic<T>
)
|
|
(C++20)
|
notifies a thread blocked in atomic_wait
(function template) |
|
(C++20)
|
notifies all threads blocked in atomic_wait
(function template) |