linux-kernel - Re: [PATCH] sched/core: Drop debugging leftover trace

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Date:	Tue, 07 Apr 2015 14:47:50 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] sched/core: Drop debugging leftover trace_printk call

On 03/04/2015 09:42, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> Commit
> 
>   3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()")
> 
> forgot a trace_printk debugging piece in and Steve's banner blew in
> dmesg. Remove it.
>

Argh! Sorry about that! Shame on me, I didn't pay much attention to
Rostedt's banner because I was working on several fixes at once :(.

Anyway, how about we add also something like this to checkpatch?
(I'll add appropriate CCs if this makes sense).

Thanks,

- Juri

>From e5733b377d55fd760160fa0e7822bdefa4f3a2c4 Mon Sep 17 00:00:00 2001
From: Juri Lelli <juri.lelli@....com>
Date: Sun, 5 Apr 2015 09:57:04 +0100
Subject: [PATCH] scripts/checkpatch: check for uses of trace_printk

Production kernels will scream if trace_printk() is used (thanks to
Rostedt's banner). Rather than waiting for that to happen, let's check
patches beforehand.

Signed-off-by: Juri Lelli <juri.lelli@....com>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d124359..1fc454c5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3257,6 +3257,12 @@ sub process {
 			     "Prefer printk_ratelimited or pr_<level>_ratelimited to printk_ratelimit\n" . $herecurr);
 		}
 
+# check for uses of trace_printk
+		if ($line =~ /\btrace_printk\s*\(/) {
+			ERROR("TRACE_PRINTK",
+			      "Never use trace_printk in production code!\n" . $herecurr);
+		}
+
 # printk should use KERN_* levels.  Note that follow on printk's on the
 # same line do not need a level, so we use the current block context
 # to try and find and validate the current printk.  In summary the current
-- 
2.3.0
 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Juri Lelli <juri.lelli@....com>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...il.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/sched/core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index a27d38f5a464..dbfc93d40292 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7015,10 +7015,8 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
>  
>  			rcu_read_unlock_sched();
>  
> -			if (overflow) {
> -				trace_printk("hotplug failed for cpu %lu", cpu);
> +			if (overflow)
>  				return notifier_from_errno(-EBUSY);
> -			}
>  		}
>  		cpuset_update_active_cpus(false);
>  		break;
> 

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