linux-kernel - Re: [PATCH 1/2] printk: Add new pr_*_deferred

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Message-ID: <20210125194602.4ayir2tmlllmrnk4@e107158-lin>
Date:   Mon, 25 Jan 2021 19:46:02 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] printk: Add new pr_*_deferred_once() variants

On 01/25/21 12:04, John Ogness wrote:
> On 2021-01-25, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Sat, Jan 23, 2021 at 11:37:40PM +0000, Qais Yousef wrote:
> >> To allow users in code where printk is not allowed.
> >> 
> >> Signed-off-by: Qais Yousef <qais.yousef@....com>
> >> ---
> >>  include/linux/printk.h | 24 ++++++++++++++++++++++++
> >>  1 file changed, 24 insertions(+)
> >> 
> >> diff --git a/include/linux/printk.h b/include/linux/printk.h
> >> index fe7eb2351610..92c0978c7b44 100644
> >> --- a/include/linux/printk.h
> >> +++ b/include/linux/printk.h
> >> @@ -480,21 +480,45 @@ extern int kptr_restrict;
> >>  	printk_once(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> >>  /* no pr_cont_once, don't do that... */
> >>  
> >> +#define pr_emerg_deferred_once(fmt, ...)				\
> >> +	printk_deferred_once(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_alert_deferred_once(fmt, ...)				\
> >> +	printk_deferred_once(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_crit_deferred_once(fmt, ...)					\
> >> +	printk_deferred_once(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_err_deferred_once(fmt, ...)					\
> >> +	printk_deferred_once(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_warn_deferred_once(fmt, ...)					\
> >> +	printk_deferred_once(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_notice_deferred_once(fmt, ...)				\
> >> +	printk_deferred_once(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
> >> +#define pr_info_deferred_once(fmt, ...)					\
> >> +	printk_deferred_once(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> >> +/* no pr_cont_deferred_once, don't do that... */
> >
> > I absolutely detest this.. the whole _deferred thing is an
> > abomination.
> 
> And it will disappear at some point.
> 
> > We should be very close to printk not needing this anymore, printk
> > people?
> 
> It will disappear once console printing threads are introduced. We
> probably still have a few kernel releases until we see that. First we
> need to finish merging full lockless access, remove the safe buffers,
> and merge the atomic consoles.

Okay. As I said in the cover letter, I didn't think the addition of these new
macros looked like a win overall.

I will drop this patch and just open code the use of printk_deferred_once() in
hrtimer_interrupt(). Which should be easier to fix later when it should
disappear.

Thanks

--
Qais Yousef