Re: [PATCH 1/3] RFC: Solved unnecessary schedule latency in the TTY layer (1/3)

[Steven Rostedt <rostedt@xxxxxxxxxxx>]

On Mon, 2012-05-14 at 14:25 +0200, Ivo Sieben wrote:

> void tty_flip_buffer_push(struct tty_struct *tty)
> {
> 	unsigned long flags;
> 	spin_lock_irqsave(&tty->buf.lock, flags);
> 	if (tty->buf.tail != NULL)
> 		tty->buf.tail->commit = tty->buf.tail->used;
> 	spin_unlock_irqrestore(&tty->buf.lock, flags);
> 
> #ifndef CONFIG_PREEMPT_RT_FULL
> 	if (tty->low_latency)
> 		flush_to_ldisc(&tty->buf.work);
> 	else
> 		schedule_work(&tty->buf.work);
> #else
> 	flush_to_ldisc(&tty->buf.work);
> #endif
> }
> 

Note, just to keep ugly #ifdefs out of C code, or at least C functions,
it is usually better to wrap the above in something like:


#ifdef CONFIG_PREEMPT_RT_FULL
static inline void tty_flush_work(struct tty_struct *tty)
{
	flush_to_ldisc(&tty->buf.work);
}
#else
static inline void tty_flush_work(struct tty_struct *tty)
{
	if (tty->low_latency)
		flush_to_ldisc(&tty->buf.work);
	else
		schedule_work(&tty->buf.work);
}
#endif


Then the C function would just look like:

void tty_flip_buffer_push(struct tty_struct *tty)
{
        unsigned long flags;
        spin_lock_irqsave(&tty->buf.lock, flags);
        if (tty->buf.tail != NULL)
                tty->buf.tail->commit = tty->buf.tail->used;
        spin_unlock_irqrestore(&tty->buf.lock, flags);

	tty_flush_work(tty);
}

-- Steve


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