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Methods that make use of await must be declared with the async keyword. In methods that have a return value of type Task<T>, methods declared with async must have a return statement of type assignable to T instead of Task<T>; the compiler wraps the value in the Task<T> generic.
As an example of the first possibility, in C++11, a thread that needs the value of a future can block until it is available by calling the wait() or get() member functions. A timeout can also be specified on the wait using the wait_for() or wait_until() member functions to avoid indefinite blocking.
In computer science and software engineering, busy-waiting, busy-looping or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input or a lock is available.
For this reason, it is usually necessary to enclose each wait operation in a loop like this while not ( P) do wait c where P is some condition stronger than P c. The operations notify c and notify all c are treated as "hints" that P may be true for some waiting thread. Every iteration of such a loop past the first represents a lost notification ...
Multiple processes or threads operate on the integer entirely in userspace (using atomic operations to avoid interfering with one another), and only resort to relatively expensive [citation needed] system calls to request operations on the wait queue (for example to wake up waiting processes, or to put the current process on the wait queue). A ...
A follow-up paper by Kogan and Petrank [20] provided a method for making wait-free algorithms fast and used this method to make the wait-free queue practically as fast as its lock-free counterpart. A subsequent paper by Timnat and Petrank [21] provided an automatic mechanism for generating wait-free data structures from lock-free ones. Thus ...
A callback is often back on the level of the original caller. In computer programming, a callback is a function that is stored as data (a reference) and designed to be called by another function – often back to the original abstraction layer.
A simple way to understand wait (P) and signal (V) operations is: wait: Decrements the value of the semaphore variable by 1. If the new value of the semaphore variable is negative, the process executing wait is blocked (i.e., added to the semaphore's queue). Otherwise, the process continues execution, having used a unit of the resource.