Double forking to prevent Zombie process
We have discussed Three methods of Zombie Prevention. This article is about one more method of zombie prevention.
Zombie Process: A process which has finished the execution but still has entry in the process table to report to its parent process is known as a zombie process. A child process always first becomes a zombie before being removed from the process table.
How Creating a Grandchild / Double Forking helps?
- The parent calls wait and creates a child. The child creates a grandchild and exits.
- The grandchild executes its instruction(task) and eventually it terminates. As the child has already exited, the grandchild will be taken care by init process.
- Init collect the exit status of grandchild. Hence the grandchild is not a zombie.
Note: Child is not a zombie as the parent called wait. Also in this case, the parent cannot verify the exit status of grandchild.
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