Date: Sun, 8 Sep 2002 18:56:55 -0700 From: Jonathan Mini <mini@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: Re: PERFORCE change 17249 for review Message-ID: <20020909015655.GZ7265@elvis.mu.org> In-Reply-To: <200209090145.g891jLMJ059559@freefall.freebsd.org>
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Great. I submitted more than I intended.
Pointy-hat to me.
> kse_yield(struct thread *td, struct kse_yield_args *uap)
> {
> + struct thread *td2;
> +
> + /* KSE-enabled processes only, please. */
> + if ((td->td_proc->p_flag & P_KSES) == 0)
> + return (EINVAL);
> +
> + /* Don't discard the last thread. */
> + td2 = FIRST_THREAD_IN_PROC(td->td_proc);
> + KASSERT(td2 != NULL, ("kse_yield: no threads in our proc"));
> + if (TAILQ_NEXT(td, td_plist) == NULL)
> + return (EINVAL);
>
> /* Abandon thread. */
> PROC_LOCK(td->td_proc);
This code disallows kse_yield() to be called from a non-KSE-process,
and in a KSE-process, does not the proc abandon the last thread
(leaving a struct proc with zero threads, which -- among other
things -- is unkillable).
As an aside, being able to rely on kse_yield() failing when there
are no other threads running lets it intelligently decide to drop
into an idle loop.
--
Jonathan Mini <mini@freebsd.org>
http://www.freebsd.org/
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