----- Original Message ---- From: Mulyadi Santosa <mulyadi.santosa@gmail.com> To: manish honap <manish_honap_vit@yahoo.co.in> Cc: kernelnewbies@kernelnewbies.org Sent: Thu, 16 June, 2011 10:45:36 AM Subject: Re: Linux kernel thread model On Thu, Jun 16, 2011 at 11:39, manish honap <manish_honap_vit@yahoo.co.in> wrote:

Hi all

Can someone please tell me what is the threading model of linux kernel ? user space thread:kernel thread process - n:1 or m:n or 1:1

1:1, that is 1 kernel process represent 1 user space thread.... more about it, google for NPTL paper written by Ulrich Drepper and Ingo Molnar. How they understand whether kernel part is scheduled or user part is scheduled ?

Hi Mulyadi, On Thu, Jun 16, 2011 at 10:37 AM, Mulyadi Santosa <mulyadi.santosa@gmail.com> wrote:

On Thu, Jun 16, 2011 at 14:06, manish honap <manish_honap_vit@yahoo.co.in> wrote:

...

How they understand whether kernel part is scheduled or user part is scheduled ?

not sure if I got your question correctly, but the one that is scheduled is the process..... 1:1 model means for single fork()/clone()/pthread_create() in user space, clone() syscall with various parameters are called in kernel space. Then, we end up creating single process. This represent that whole single thread.

A few clarifications. I like to think of a process as a memory space, and a thread as a unit of execution. Many processes have a single thread, but processes can have mutliple threads as well. Each thread has a kernel side and a user-mode side. The kernel mode portion has its own stack which is separate from the user-mode stack, but you can think of them all together as being a single thread. You can view all of the processes in the system by using ls -d /proc/[0-9]* You can view all of the threads in the system by using ls -d /proc/[0-9]*/task/* Due to historical reasons, we have some confusing terminology which is different between kernel space and user-space. The numbers under the task directory are called tids in user-space, but are called pids in kernel space (i.e. current->pid) The numbers under the proc directory are called pids in user-space, but are called tgid in kernel space (i.e. current->tgid) When running in kernel space, the kernel component of the thread runs (so the kernel thread-stack is used). When running in user-space, the user component of the thread tuns (so the user-space stack is used). When scheduling, you're scheduling the thread as a whole, and not the kernel-side or user-side component. If you write a driver or loadable module, you can create kernel threads which have no user-mode portion, but you can't create a user-mode thread which doesn't have a kernel side component. kernel mode threads appear to be their own process, which is where my process=memory space model break down, but for user space it holds. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com