Re: [ANNOUNCE] Linux 2.6 Real Time Kernel

[Måns Rullgård]

Sven-Thorsten Dietrich <sdietrich@xxxxxxxxxx> 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?

-- 
Måns Rullgård
mru@xxxxxxxxxx

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