CODEWITHSUNDEEP
linuxlinux-kernelsystem-calls
Tim
Tim

Reputation: 99508

Why is `kernal_thread()` not listed as a system call of Linux?

I was wondering why kernal_thread() isn't listed as a system call in http://man7.org/linux/man-pages/man2/syscalls.2.html?

Does a Linux application programmer never have any need to create a kernel thread?

Is the function accessible to a Linux application programmer?

Thanks.

Upvotes: 0

Views: 364

Answers (2)

Jitender
Jitender

Reputation: 411

As you are familiar that their are two address spaces one user and kernel, normal function will run in user space but when you will make use of some function calls that are implemented in kernel space you cannot use them directly so to access them we need system calls.

So now your question is why kernal_thread() is not listed in system calls.

(As answered by "that other guy" ) kernal_thread() function are used by the kernel programmer or usual in device driver for creating thread in kernel space. So their implementation is in kernel space and only used by kernel developer or programer. (Note:- if a interface have been provided for some function for user space that will be concluded as system call, as no interface for that function for user so their is no documentation for that in man pages)

If you want to read about documents about Kernel space function download the kernel source and check the "Documentation" folder or check the source for respective function they have few comments.

Upvotes: 1

that other guy
that other guy

Reputation: 123570

Application programmers often need to create "kernel scheduled threads", aka "OS threads" or "native threads" using the clone syscall from that list.

"Kernel threads", however, are just threads that the kernel uses to run kernel code for its own internal purposes. They are created and used by kernel context code only. Each piece of software is responsible for creating and managing its own threads to do its own job, including userspace applications and the kernel itself.

kernel_thread is a kernel function defined in kernel/fork.c, which is not exposed to userspace. It's part of the internal kernel API and not a syscall.

Upvotes: 3

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