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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>
References: <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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