Re: [PATCH 1/2] printk: Add new pr_*_deferred_once() variants

[John Ogness <john.ogness@linutronix.de>]

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