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SubjectRe: [PATCH v4 3/3] media: atomisp: Only use trace_printk if allowed
On Thu, 20 Aug 2020 19:36:19 -0700
Joe Perches <joe@perches.com> wrote:

> On Thu, 2020-08-20 at 21:57 -0400, Steven Rostedt wrote:
> > On Fri, 21 Aug 2020 09:39:19 +0800
> > Nicolas Boichat <drinkcat@chromium.org> wrote:
> []
> > > Some other approaches/ideas:
> > > 1. Filter all lkml messages that contain trace_printk. Already found
> > > 1 instance, and I can easily reply to those with a semi-canned answer,
> > > if I remember to check that filter regularly (not sustainable in the
> > > long run...).
> >
> > Added Joe Perches to the thread.
> >
> > We can update checkpatch.pl to complain about a trace_printk() that it
> > finds in the added code.
>
> Why?
>
> I don't see much value in a trace_printk checkpatch warning.
> tracing is still dependent on CONFIG_TRACING otherwise
> trace_printk is an if (0)
>
> ELI5 please.
>

Because no production code should contain trace_printk(). It should be
deleted before going to Linus. If you have trace_printk() in your code,
you will be greeted by the following banner in your dmesg:

**********************************************************
** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
** **
** trace_printk() being used. Allocating extra memory. **
** **
** This means that this is a DEBUG kernel and it is **
** unsafe for production use. **
** **
** If you see this message and you are not debugging **
** the kernel, report this immediately to your vendor! **
** **
** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
**********************************************************

-- Steve

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