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SubjectRe: SCO: "thread creation is about a thousand times faster than on native Linux"
On Wed, Aug 23, 2000 at 09:54:55PM -0700, Linus Torvalds wrote:
>
>
> On Thu, 24 Aug 2000, Albert D. Cahalan wrote:
> >
> > Nobody will send you a sane patch without you at least hinting
> > at what you might like to see. I'm sure many of us would be happy
> > to write the code, but not under the expectation that it will
> > be rejected.
>
> Acceptable solution:
> - add "tgid" (thread group ID) to "struct task_struct"
> - CLONE_PID will leave tgid unchanged.
> - non-CLONE_PID will set "tgid" to the same as pid
> - get_pid() checks that the new pid is not the tgid of any process.
>
> Basically, the above creates a new "session pid" for the collection of
> threads. This is nothing new: the above is basially _exactly_ the same as
> p->pgrp and p->session, so it fits quite well into the whole pid notion.
>
> It also means that "current->pid" basically becomes a traditional "thread
> ID", while "current->tgid" effectively becomes what pthreads calls a
> "pid". Except Linux does it the right way around, ie the same way we've
> done sessions and process groups. Because, after all, this _is_ just a
> process group extension.
>
> Now, once you have a "tgid" for each process, you can add system calls to
> - sys_gettgid(): get the thread ID
> - sys_tgkill(): do a pthreads-like "send signal to thread group" (or
> extend on the current sys_kill())
>
> Now, the problem is that the thread group kill thing for true POSIX
> threads signal behaviour probably has to do some strange magic to get the
> pthreads signal semantics right. I don't even know the exact details here,

How about allowing the thread root process to do all that junk by giving it
raw signals - e.g. delivering SUSPEND - and then letting it distribute
via a pthread_kill?


--
---------------------------------------------------------
Victor Yodaiken
Finite State Machine Labs: The RTLinux Company.
www.fsmlabs.com www.rtlinux.com

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