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Date: Wed, 4 Sep 2024 14:15:13 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Leonardo Bras <leobras@redhat.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Rik van Riel <riel@surriel.com>,
	Thorsten Blum <thorsten.blum@toblux.com>,
	Zqiang <qiang.zhang1211@gmail.com>, Tejun Heo <tj@kernel.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Caleb Sander Mateos <csander@purestorage.com>,
	linux-kernel@vger.kernel.org,
	"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
	Chen Yu <yu.c.chen@intel.com>, Julia Lawall <Julia.Lawall@inria.fr>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [RFC PATCH v2 4/5] softirq: Unify should_wakeup_ksoftirqd()
Message-ID: <20240904121513.GH4723@noisy.programming.kicks-ass.net>
References: <20240904111223.1035-1-kprateek.nayak@amd.com>
 <20240904111223.1035-5-kprateek.nayak@amd.com>
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In-Reply-To: <20240904111223.1035-5-kprateek.nayak@amd.com>

On Wed, Sep 04, 2024 at 11:12:22AM +0000, K Prateek Nayak wrote:

> @@ -118,14 +101,40 @@ EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context);
>   * the task which is in a softirq disabled section is preempted or blocks.
>   */
>  struct softirq_ctrl {
> +#ifdef CONFIG_PREEMPT_RT
>  	local_lock_t	lock;
> +#endif
>  	int		cnt;
>  };
>  
> -static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
> +static DEFINE_PER_CPU_ALIGNED(struct softirq_ctrl, softirq_ctrl) = {
> +#ifdef CONFIG_PREEMPT_RT
>  	.lock	= INIT_LOCAL_LOCK(softirq_ctrl.lock),
> +#endif
>  };

With the exception of CONFIG_DEBUG_LOCK_ALLOC (part of LOCKDEP)
local_lock_t is an empty structure when PREEMPT_RT=n.

That is to say, you can probably get by without those extra #ifdefs.