Re: [ANNOUNCE] v5.14-rc4-rt4

From: Steven Rostedt <rostedt@goodmis.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	Peter Zijlstra <peterz@infradead.org>,
	Daniel Wagner <wagi@monom.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-rt-users@vger.kernel.org
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4
Date: Wed, 4 Aug 2021 12:47:55 -0400	[thread overview]
Message-ID: <20210804124755.21ca7e3d@oasis.local.home> (raw)
In-Reply-To: <20210804163119.t4c7bkpdk33byxtx@linutronix.de>

On Wed, 4 Aug 2021 18:31:19 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> CPU-local wake-ups just set NEED_RESCHED and wait for preempt_enable()
> to do the magic. Just because the code not perform wake_up() now does
> not mean it will not do so in the future. Also it is here as an example
> which might be copied somewhere else.

Does this mean all local_irq_disable/enable() is audited? What do you do for;

	local_irq_disable();
	[..]
	wakeup_process(x); /* on local CPU */
	[..]
	local_irq_enable();

And if local_irq_disable() is not used anymore, or seldom, what harm
would it be to add a preemption check to that caller? And change
local_irq_enable() that is used internally by other atom functions be
called __local_irq_enable()?

Not to mention that we could just open code that too:

	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
		local_irq_enable();
		preempt_check_resched();
	}

And make it ugly enough that nobody will want to copy it :-)

-- Steve