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Few people may realize that after a process calls exit, the process does not disappear immediately, but leaves a data structure called Zombie. Among the five States of a Linux Process, a zombie process is a very special one. It has abandoned almost all the memory space, no executable code, and cannot be scheduled. Few people may realize that a process callsExAfter it, the process does not disappear immediat

Here's what I read about 11 years ago in Apue (Advanced Programming for UNIX environments) to understand the orphan process and the zombie process, and to make it easier to remember and explain it in a figurative way. (not necessarily accurate, but I'll post a professional explanation on Wikipedia.) ) Os os like a company, the CEO of the company is the INIT process. Any child process has a parent process, just like any one has a father. T

This gives only the concept of the zombie process and the orphan process. SOURCE "In-depth understanding of the computer system (original book 3rd edition)" and online blog, the following will give a blog source.Introduction: Recycling of sub-processesWhen a process terminates for some reason, the kernel does not immediately purge it from the system. Instead, the process is kept in a terminated state until it is reclaimed by its parent process (reaped

Speaking of fork, you have to mention cow (copy on write), which is "copy on write". That is, when the fork occurs, the child process simply does not copy the parent process's memory page, but shares it with the parent process. When a child process or parent process needs to modify a memory page, Linux copies the memory page to the modifier and then modifies it so that the parent-child process does not share any memory from the user's point of view. Cow is the process to write the shared memory

Botnets In the previous article, we have understood the concepts of parent and child processes, and have mastered the usage of System Call exit, but few people may realize that, after a process calls exit, it does not disappear immediately, but leaves a data structure called Zombie.Among the five States of a Linux Process, a zombie process is a very special one. It has abandoned almost all the memory space, no executable code, and cannot be scheduled,

The zombie process in the Linux system and the zombies in the real world (although I have not seen it) are similar, although they are dead, but because no one gives them a corpse, they can walk around. A zombie process is a process that has been terminated, but still retains some information, waiting for its parent process to bury it. How did the zombie process o

Orphan process: One parent process exits, and one or more of its child processes are still running, then those child processes will become orphans. The orphan process will be adopted by the INIT process (process number 1) and the Init process completes the state collection for them.Zombie Process: A process uses fork to create a child process, and if the child process exits, and the parent process does not call wait or waitpid to get state information for the child process, the process descripto

PS --forest ASCII Art process tree 2 How to clear the zombie process:1. Rewrite the parent process and bury it after the child process dies. The concrete approach is to take over the SIGCHLD signal. After the child process dies, the SIGCHLD signal is sent to the parent process, and after the parent process receives this signal, the waitpid () function is executed to corpse the child process.This is based on the principle that even if the parent proces

a damaged pointer back and forth in the application, it does not crash. A crash occurs when an application attempts to reference a damaged pointer.5. Zombie Debug ModeThe zombie debug mode has gained popularity over the last few years, and in fact they have been on Xcode for more than 10 years. Zombies sound a little dramatic, but it's actually a great name to help us debug the exc_bad_access feature. Let

Few people may realize that after a process calls exit, the process does not disappear immediately, but leaves a data structure called Zombie. Among the five Linux processes, the zombie process is a very special one. it has abandoned almost all the memory spaces... Few people may realize that after a process calls exit, the process does not disappear immediately, but leaves a data structure called

What is a zombie process ?First the kernel releases all the stores used by the terminating process (called the exit system call), closes all open files, and so on, but the kernel holds a certain amount of information for each terminating child process. This information includes at least the process ID, the terminating state of the process, and the CPU time used by the process, so this information is available when the parent process that terminates th

Orphan process and zombie processAfter the normal child processes fork their parent process, they establish a parent-child relationship.When the child process is terminated, it notifies the parent process and empties the memory it occupies and leaves its own exit message in the kernel (exit code, 0 if it runs smoothly, or an integer that is >0 if there is an error or an exception condition). In this message, it explains why the process exited. When th

Zombie Processes (Zombie process)The process has run to the end, but the resource occupied by the process is not recycled, and such a process is called a zombie process . at the time each process exits, the kernel frees all resources of the process, including open files, memory used, and so on. However , it still retains certain information, which mainly refers

1. What is a zombie processIf the parent process terminates before the child process, all the parent processes of the child processes will be changed to the INIT process, which we call the INIT process adopted. You can see that the parent process of the child process Ppid has changed to 1 by using the PS command.When a child process terminates before the parent process, the kernel holds a certain amount of information for each terminating child proces

How to view zombie processes on Linux systems, how many zombie processes are counted?#ps-ef | grep defunctOr looking for a process with a status of Z, Z is the meaning of the zombie process representing zombie process.In addition, using the top command to view a column is S, if the status of Z indicates that it is a

Orphan process and zombie processI. Definition: What is orphan process and zombie processZombie Process: A child process exits if its parent process has not yet called wait () or waitpid (). This child process is the zombie process.Orphan process: One parent process exits, and one or more of its child processes are still running, then those child processes will b

Zombie process (zombie process ):When a process stops running (exit), all its resources and memory space will be released for use by other processes; however, it retains a record in the Process Table of the OS kernel, including the process ID, exit status, and running time of the process. This information is convenient for the parent process of the process to obtain its exit status at any time (that is, why

Zombie Processes (Zombie process) The process has run to the end, but the resource occupied by the process is not recycled, and such a process is called a zombie process . At the time each process exits, the kernel frees all resources of the process, including open files, memory used, and so on. however , it still retains certain information, w

A description of the zombie process is first transcribed online:Zombie Process: A process uses fork to create a child process, and if the child process exits, and the parent process does not call wait or waitpid to get state information for the child process, the process descriptor of the child process is still stored in the system. This process is called a zombie process. At the time each process exits, th

Zombie objects are useful for our debugger, and the way to open a zombie object in Xcode is to set the nszombieenabled environment variable to Yes, which causes all objects to be freed, the program will run for a long time, and this time we'll write some code, Emulate the implementation in Xcode, so that we can generally understand the principle of implementing a Zombie