linux-kernel - Re: [PATCH next v2 1/2] dump_stack: move cpu lock to printk.c

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Message-ID: <YL+EwqLO8KsGqQVm@alley>
Date:   Tue, 8 Jun 2021 16:54:58 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH next v2 1/2] dump_stack: move cpu lock to printk.c

On Tue 2021-06-08 15:55:35, John Ogness wrote:
> On 2021-06-08, Petr Mladek <pmladek@...e.com> wrote:
> > Reviewed-by: Petr Mladek <pmladek@...e.com>
> >
> >> --- a/kernel/printk/printk.c
> >> +++ b/kernel/printk/printk.c
> >> @@ -3532,3 +3532,78 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
> >> +void printk_cpu_lock_irqsave(bool *lock_flag, unsigned long *irq_flags)
> >> +{
> >> +	int old;
> >> +	int cpu;
> >> +
> >> +retry:
> >> +	local_irq_save(*irq_flags);
> >> +
> >> +	cpu = smp_processor_id();
> >> +
> >> +	old = atomic_cmpxchg(&printk_cpulock_owner, -1, cpu);
> >> +	if (old == -1) {
> >> +		/* This CPU is now the owner. */
> >> +
> >
> > Superfluous space?
> 
> I was concerned that people may associate the comment with the following
> line of code. Especially in the next patch when many more lines are
> added. The comment is for the whole conditional block.
> 
> >> +		*lock_flag = true;
> >
> > The original name name "was_locked" was more descriptive. I agree that
> > it was not good for an API. What about keeping the inverted logic and
> > calling it "lock_nested" ?
> >
> > I do not resist on any change. The logic is trivial so...
> 
> I wanted it to be an opaque variable, which is why it is named so. But I
> can rename it for v3. There is no need to debate naming here.

Yup. I didn't want to block the patch because of this. I mentioned it
just for case v3 was needed and you agreed. Feel free to keep your
preferred names and spacing. I am not going to fight over it.

Best Regards,
Petr