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In computer operating systems, a process (or task) may wait for another process to complete its execution. In most systems, a parent process can create an independently executing child process . The parent process may then issue a wait system call , which suspends the execution of the parent process while the child executes.
wait normally returns the exit status of the last job which terminated. It may also return 127 in the event that n specifies a non-existent job or zero if there were no jobs to wait for. Because wait needs to be aware of the job table of the current shell execution environment, it is usually implemented as a shell builtin .
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.
In programs that never end (such as operating systems), infinite busy waiting can be implemented by using unconditional jumps as shown by this NASM syntax: jmp $. The CPU will unconditionally jump to its own position forever. A busy wait like this can be replaced with:
Steps 1a and 1b can occur in either order, with 1c usually occurring after them. While the thread is sleeping and in c's wait-queue, the next program counter to be executed is at step 2, in the middle of the "wait" function/subroutine. Thus, the thread sleeps and later wakes up in the middle of the "wait" operation.
The underlying program is no longer executing, but the process remains in the process table as a zombie process until its parent process calls the wait system call to read its exit status, at which point the process is removed from the process table, finally ending the process's lifetime.
Some QVC shoppers can’t help but make a connection with some of the network’s products — and hosts. Over the years, viewers have developed close bonds with longtime program hosts who have a ...
The parent process can either continue execution or wait for the child process to complete. The child, after discovering that it is the child, will most often then replace itself completely with another program, so that the code and address space of the original program are lost. This replacement is, however, a choice of the architecture one ...