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From:   John Ogness <john.ogness@linutronix.de>
To:     Peter Zijlstra <peterz@infradead.org>,
        Qais Yousef <qais.yousef@arm.com>
Cc:     Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] printk: Add new pr_*_deferred_once() variants
In-Reply-To: <YA6fTuFEaCjFQB3h@hirez.programming.kicks-ass.net>
References: <20210123233741.3614408-1-qais.yousef@arm.com> <20210123233741.3614408-2-qais.yousef@arm.com> <YA6fTuFEaCjFQB3h@hirez.programming.kicks-ass.net>
Date:   Mon, 25 Jan 2021 12:04:01 +0106
Message-ID: <87y2gh2shy.fsf@jogness.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On 2021-01-25, Peter Zijlstra <peterz@infradead.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@arm.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.

John Ogness