>
> On Fri, Mar 18, 2005 at 09:16:29AM -0500, Gopu Bhaskar hit keys to
> express the following:
> >
> > > > > There is nothing that prevents me from creating a user thread
> > > > without using CLONE_VM. If i specify CLONE_VM to clone system
> > > > call it only makes things faster. I strongly believe that user
> > > > thread and kernel thread should be distinguished from each other.
> > ^^^^^^^^^ Sorry I made a typo
> > here, I meant "should not be"
> At what level should this distinction (not) be made?
Sorry for all the confusion all I wanted to write was that processes
and so called user threads should not be distingushed from each other.
> Kernel threads cannot access user space at all. They are just for
> kernel tasks.
> There is a marked and clear distinction between both of these. For
> example, when
> a kernel thread is created, kernel_thread() hand crafts a pt_regs
> structure and
> call do_fork(). They cannot be traced (CLONE_UNTRACED).
> > > > The term user thread is implementation specific. Mostly clone
> I agree with you here. But in linux, the kernel (to keep matters simple and
> elegant) has taken a stance of being agnostic to differences
> between threads and
> processes.
> > > > system call is used for creating threads. see man clone. You
> > > > would find that you can create threads that share everything else
> > > > but VM.
> What do you mean? Threads do not share VM?
This is what the clone man page says.
If CLONE_VM is not set, the child process runs in a
separate copy of the memory space of the calling
process at the time of clone. Memory writes or
file mappings/unmappings performed by one of the
processes do not affect the other, as with fork
>
> --
> "The significant owl hoots in the night."
> (Guards! Guards!)
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