[PATCH v2] scripts/checkpatch: check for uses of trace_printk

[Juri Lelli <juri.lelli@arm.com>]

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

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: linux-kernel@vger.kernel.org
---
Changes since v1:

 o added an exception when the code is in kernel/trace/, as suggested
   by Steve and Joe;

 scripts/checkpatch.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d124359..c36b2b7 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3257,6 +3257,13 @@ sub process {
 			     "Prefer printk_ratelimited or pr_<level>_ratelimited to printk_ratelimit\n" . $herecurr);
 		}
 
+# check for uses of trace_printk
+		if ($realfile !~ m@kernel/trace/@ &&
+		    $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