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

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Message-ID: <20210804124755.21ca7e3d@oasis.local.home>
Date:   Wed, 4 Aug 2021 12:47:55 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Wagner <wagi@...om.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4

On Wed, 4 Aug 2021 18:31:19 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.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