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Concept
Parent process
Résumé
In computing, a parent process is a process that has created one or more child processes.
In Unix-like operating systems, every process except process 0 (the swapper) is created when another process executes the fork() system call. The process that invoked fork is the parent process and the newly created process is the child process. Every process (except process 0) has one parent process, but can have many child processes.
The operating system kernel identifies each process by its process identifier. Process 0 is a special process that is created when the system boots; after forking a child process (process 1), process 0 becomes the swapper process (sometimes also known as the "idle task"). Process 1, known as , is the ancestor of every other process in the system.
In the Linux kernel, in which there is a very slim difference between processes and POSIX threads, there are two kinds of parent processes, namely real parent and parent. Parent is the process that receives the SIGCHLD signal on child's termination, whereas real parent is the thread that actually created this child process in a multithreaded environment. For a normal process, both these two values are same, but for a POSIX thread which acts as a process, these two values may be different.
Zombie process
The operating system maintains a table that associates every process, by means of its process identifier (generally referred to as "pid") to the data necessary for its functioning. During a process's lifetime, such data might include memory segments designated to the process, the arguments it's been invoked with, environment variables, counters about resource usage, user-id, group-id and group set, and maybe other types of information.
When a process terminates its execution, either by calling exit (even if implicitly, by executing a return command from the main function) or by receiving a signal that causes it to terminate abruptly, the operating system releases most of the resources and information related to that process, but still keeps the data about resource utilization and the termination status code, because a parent process might be interested in knowing if that child executed successfully (by using standard functions to decode the termination status code) and the amount of system resources it consumed during its execution.
Source officielle
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Proximité ontologique
Séances de cours associées (6)
Processus : Aperçu et gestion
Couvre les bases des processus dans les systèmes d'exploitation, y compris la création, la mise en page de la mémoire, les transitions d'état, la virtualisation, les API et l'exécution de programmes.
Publications associées (4)
QMMMW: A wrapper for QM/MM simulations with QUANTUM ESPRESSO and LAMMPS
We present QMMMW, a new program aimed at performing Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics. The package operates as a wrapper that patches PWscf code included in the QUANTUM ESPRESSO distribution and LAMMPS Molecular Dynamics Simu ...
Elsevier Science Bv2015Concepts associés (13)
Daemon (informatique)
Un daemon (prononcé ou , du grec - divinité), mot anglais qui signifie « daimôn », souvent traduit erronément par démon, est un type de programme informatique, un processus ou un ensemble de processus qui s'exécute en arrière-plan plutôt que sous le contrôle direct d'un utilisateur. Le terme daemon semble être introduit en 1963 par les concepteurs de CTSS du MIT, en réponse au « dragon », terme employé par les concepteurs d'ITS.
Exit (system call)
On many computer operating systems, a computer process terminates its execution by making an exit system call. More generally, an exit in a multithreading environment means that a thread of execution has stopped running. For resource management, the operating system reclaims resources (memory, , etc.) that were used by the process. The process is said to be a dead process after it terminates. Under Unix and Unix-like operating systems, a process is started when its parent process executes a fork system call.
Wait (system call)
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. 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.