RFC: set the thread name

[Stefani Seibold <stefani@seibold.net>]

Currently it is not easy to identify a thread in linux, because there is
no thread name like in some other OS. 

If there were are thread name then we could extend a kernel segv message
and the /proc/<pid>/task/<tid>/... entries by a TName value like this:

cat /proc/492/task/495/status
Name:   test
TName:  RX-Data          <- this is the thread identification field
State:  S (sleeping)
Tgid:   492
Pid:    495
PPid:   1
.
.
.

This will it make much easier to determinate which thread id is
associated to a logical thread.

It would be possible do this without add a new entry to the task_struct.
Just use the comm entry which is available, because it has the same
value as the group_leader->comm entry.

The only thing to do is to replace all task_struct->comm access by
task_struct->group_leader->comm to have the old behavior. This can be
eventually encapsulated by a macro.

The task_struct->comm of a non group_leader would be than the name of
the thread.

The only drawback is that there are a lot of files which must be
modified. A quick
 find linux-2.6.30 -type f | xargs grep -l -e "->comm\>"  | wc -l
shows 215 files. But this can be handled.

So i propose a new system call to give a thread a name.

What do you think?

Greetings,
Stefani