Re: [PATCH net-next] net: dev: Always serialize on Qdisc::busylock in __dev_xmit_skb() on PREEMPT_RT.

On Mon, 13 Dec 2021 11:45:59 +0100 Sebastian Andrzej Siewior wrote:

On 2021-12-10 20:32:56 [-0800], Jakub Kicinski wrote:

quoted

On Fri, 10 Dec 2021 16:41:44 +0100 Sebastian Andrzej Siewior wrote:  

quoted

-	contended = qdisc_is_running(q);
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+		contended = qdisc_is_running(q);
+	else
+		contended = true;  

Why not:

	contended = qdisc_is_running(q) || IS_ENABLED(CONFIG_PREEMPT_RT);  

I could do that. But I would swap the two arguments so that the
IS_ENABLED macro comes first and if true qdisc_is_running() is optimized
away.

FWIW I disagree. My version was more readable. The sprinkling of the
PREEMPT_RT tosh is getting a little annoying. Trying to regress the 
clarity of the code should be top of mind here.