Date: Tue, 6 May 2003 00:30:46 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: David Xu <davidxu@freebsd.org> Cc: Daniel Eischen <eischen@pcnet1.pcnet.com> Subject: Re: kern_threads.c.. upcall question.. Message-ID: <Pine.BSF.4.21.0305060026570.4662-100000@InterJet.elischer.org> In-Reply-To: <001901c313a1$01c97c30$f001a8c0@davidw2k>
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On Tue, 6 May 2003, David Xu wrote:
>
> ----- Original Message -----
> From: "Julian Elischer" <julian@elischer.org>
> To: "David Xu" <davidxu@freebsd.org>
> Cc: "Daniel Eischen" <eischen@pcnet1.pcnet.com>; <threads@freebsd.org>
> Sent: Tuesday, May 06, 2003 3:10 PM
> Subject: Re: kern_threads.c.. upcall question..
>
>
> >
> >
> > On Tue, 6 May 2003, David Xu wrote:
> >
> > > I think the following patch is enough:
> >
> > I agree that this seems enough from what I was reading.
> > (I like patches that have most lines starting with '-' :-)
> >
> >
> > >
> > > Index: kern_thread.c
> > > ===================================================================
> > > RCS file: /home/ncvs/src/sys/kern/kern_thread.c,v
> > > retrieving revision 1.129
> > > diff -u -r1.129 kern_thread.c
> > > --- kern_thread.c 1 May 2003 12:16:06 -0000 1.129
> > > +++ kern_thread.c 6 May 2003 06:32:10 -0000
> > > @@ -721,41 +721,6 @@
> > [...]
> > > void
> > > @@ -962,27 +927,25 @@
> > > uintptr_t mbx;
> > > void *addr;
> > > int error,temp;
> > > - ucontext_t uc;
> > > + mcontext_t mc;
> > >
> > > p = td->td_proc;
> > > kg = td->td_ksegrp;
> > >
> > > /* Export the user/machine context. */
> > > - addr = (void *)(&td->td_mailbox->tm_context);
> > > - error = copyin(addr, &uc, sizeof(ucontext_t));
> > > - if (error)
> > > - goto bad;
> > > -
> > > - thread_getcontext(td, &uc);
> > > - error = copyout(&uc, addr, sizeof(ucontext_t));
> > > - if (error)
> > > + get_mcontext(td, &mc, 0);
> >
> > I think this could be optimised even more.
> > (why copy the FP regs if they are not valid) (etc).
> > but it is an improvement..
> >
>
> Why need we an intermediate mcontext_t, why not
> direct copy the context in trap frame to userland space?
> This should be fastest. :-)
this is what I was thinking..
get_mcontext_user(td, addr)
[...]
>
>
> > > + addr = (void *)(&td->td_mailbox->tm_context.uc_mcontext);
> > > + error = copyout(&mc, addr, sizeof(mcontext_t));
> > > + if (error)
> > > goto bad;
> > >
> > > /* Exports clock ticks in kernel mode */
> > > addr = (caddr_t)(&td->td_mailbox->tm_sticks);
> > > temp = fuword(addr) + td->td_usticks;
> > > - if (suword(addr, temp))
> > > + if (suword(addr, temp)) {
> > > + error = EFAULT;
> > > goto bad;
> > > + }
> > >
> > > /* Get address in latest mbox of list pointer */
> > > addr = (void *)(&td->td_mailbox->tm_next);
> > >
> > >
> > > And should we disable single threading testing or do
> > > double checking in thread_user_enter()? I think per-syscall
> > > PROC_LOCK is too expensive for us.
> >
> > I am not sure which one you refer too.. Which single_threading
> > test?
> >
> Single threading testing in thread_user_enter(), someone put
> a PROC_LOCK, quoted here:
> /*
> * First check that we shouldn't just abort.
> * But check if we are the single thread first!
> */
> PROC_LOCK(p);
> if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
> mtx_lock_spin(&sched_lock);
> thread_stopped(p);
> thread_exit();
> /* NOTREACHED */
> }
> PROC_UNLOCK(p);
>
> > BTW, I am a little unsure about the calling of thread_user_enter()
> > from thread_userret().
> >
>
> This is quantum preemptive for userland, it is used when statclock
> interrupt hit in userland, if thread quantum is exhausted,
> it must unbind upcall from current thread, and schedule an upcall,
> you can think it is an implicit syscall triggered by CPU automatically
> which just means to swap out current thread.
ah..
I was thinking that we could delay most of thread_user_enter()
until we need it..
i.e why read the mailbox until we need it..
>
> >
> >
> > >
> > > David Xu
> > >
> > >
> > >
> >
> >
>
>
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