To: linux-kernel@vger.kernel.org
From: =?iso-8859-1?q?M=E5ns_Rullg=E5rd?= <mru@mru.ath.cx>
Subject: Re: [ANNOUNCE] Linux 2.6 Real Time Kernel
Date: Sat, 09 Oct 2004 12:51:02 +0200
Message-ID: <yw1x3c0orwq1.fsf@mru.ath.cx>
References: <41677E4D.1030403@mvista.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Security Through
 Obscurity, linux)
Cancel-Lock: sha1:3PszU6VGpHd6BDUXRGYG5P3HJY0=
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1216
Lines: 27

Sven-Thorsten Dietrich <sdietrich@mvista.com> writes:

> +#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT)
> +/*
> + * This could be a long-held lock.  If another CPU holds it for a long time,
> + * and that CPU is not asked to reschedule then *this* CPU will spin on the
> + * lock for a long time, even if *this* CPU is asked to reschedule.
> + *
> + * So what we do here, in the slow (contended) path is to spin on the lock by
> + * hand while permitting preemption.
> + *
> + * Called inside preempt_disable().
> + */
> +
> +/* these functions are only called from inside spin_lock
> + * and old_write_lock therefore under spinlock substitution
> + * they will only be passed old spinlocks or old rwlocks as parameter
> + * there are no issues with modified mutex behavior here. */
> +
> +#endif /* defined(CONFIG_SMP) && defined(CONFIG_PREEMPT) */

May I inquire as to the purpose of placing a couple of comments under
an #ifdef?

-- 
M?ns Rullg?rd
mru@mru.ath.cx

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/