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A "ready" or "waiting" process has been loaded into main memory and is awaiting execution on a CPU (to be context switched onto the CPU by the dispatcher, or short-term scheduler). There may be many "ready" processes at any one point of the system's execution—for example, in a one-processor system, only one process can be executing at any one ...
Ready (ready to be executed); Blocked (waiting for an event, I/O for example). Most tasks are blocked or ready most of the time because generally only one task can run at a time per CPU core. The number of items in the ready queue can vary greatly, depending on the number of tasks the system needs to perform and the type of scheduler that the ...
The parent process may then issue a wait system call, which suspends the execution of the parent process while the child executes. When the child process terminates, it returns an exit status to the operating system, which is then returned to the waiting parent process. The parent process then resumes execution.
When the operating system creates a new process, that process is initially labeled as NOT RUNNING, and is placed into a queue in the system in the NOT RUNNING state. The process (or some portion of it) then exists in main memory , and it waits in the queue for an opportunity to be executed.
When a process is created (initialized or installed), the operating system creates a corresponding process control block, which specifies and tracks the process state (i.e. new, ready, running, waiting or terminated). Since it is used to track process information, the PCB plays a key role in context switching. [1]
The operating system keeps its processes separate and allocates the resources they need, so that they are less likely to interfere with each other and cause system failures (e.g., deadlock or thrashing). The operating system may also provide mechanisms for inter-process communication to enable processes to interact in safe and predictable ways.
Then the operating system calls the switch() routine to first save the general-purpose user registers of A onto A's kernel stack, then it saves A's current kernel register values into the PCB of A, restores kernel registers from the PCB of process B, and switches context, that is, changes kernel stack pointer to point to the kernel stack of ...
An example is "blocking on a channel" where passively waiting for the other part (i.e. no polling or spin loop) is part of the semantics of channels. [3] Correctly engineered, any of these may be used to implement reactive systems. [clarification needed] Deadlock means that processes pathologically wait for each other in a circle. As such it is ...