Problem about process vs. thread in Linux

1> Light-weight processes(created by Linux-specific clone()) share address space with parent process and they and the parent process is in charge of kernel thread. Right? If YES, may user control(set,change and etc.) the priority of each light-process? If YES, how to control the priority of each light-weight process?

2> User process have individual address space and is in charge of kernel thread one-to-one. And user process may create several threads(complying to POSIX) and each such thread is in charge of one kernel thread. So, how to control the priority of each thread?

1. Clone also creates process, although with shared resources, as I know. man clone .

1. man setpriority .

Originally Posted by raskin 1. Clone also creates process, although with shared resources, as I know. man clone . 1. man setpriority .

Light-weight process have same attributes as user process except for sharing address space and resource. Am I correct?

There isn't really anything like a LWP in Linux, as I understand it. Everything is a standard process. However, because of the semantics of clone "processes" can share their entire address space and other stuff (signal handlers etc.). This makes "processes" that do this indistinguishable from a multithreaded application (in fact the PID is really just a thread group ID so a multithreaded process is really just a collection of threads that happen to be in the same thread group).

Compare these semantics to an OS like Solaris that has explicit threading support and LWPs built into the kernel.

Therefore, LWP and user process have same priority control attribute because kernel tasks serving user process or LWP is unaware which type of process is served. Right?
All LWP and their parent process have same PID(group ID). Thus how to distinct each LWP in controling their priority? Do LWP have thread ID?

Where are LWP's?? They are not created by clone. Clone-d threads are processes - they have pid's.

Originally Posted by raskin Where are LWP's?? They are not created by clone. Clone-d threads are processes - they have pid's.

Here we may think of LWP as thread with own PID. What about your opinion?

Like I said, in Linux there's no such thing as a LWP (Lightweight Process). Everything is a thread. Some threads may share a PID, memory space, etc., but that's it. Threads are scheduled equally. You might find this page helpful in understanding some of the differences.