linux-kernel - Re: [PATCH v3 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

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Message-ID: <20251218124326.22334325@gandalf.local.home>
Date: Thu, 18 Dec 2025 12:43:26 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Yury Norov <yury.norov@...il.com>
Cc: Randy Dunlap <rdunlap@...radead.org>, Andrew Morton
 <akpm@...ux-foundation.org>, Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, Christophe Leroy <chleroy@...nel.org>,
 Ingo Molnar <mingo@...nel.org>, Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, David Laight
 <david.laight@...box.com>, Petr Pavlu <petr.pavlu@...e.com>, Andi Shyti
 <andi.shyti@...nel.org>, Rodrigo Vivi <rodrigo.vivi@...el.com>, Tvrtko
 Ursulin <tursulin@...ulin.net>, Daniel Gomez <da.gomez@...nel.org>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-modules@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 4/4] tracing: move tracing declarations from kernel.h
 to a dedicated header

On Thu, 18 Dec 2025 12:33:49 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 17 Dec 2025 22:59:33 -0500
> Yury Norov <yury.norov@...il.com> wrote:
> 
> > I deem to drop trace_printk.h from kernel.h - it is more aligned with
> > the idea of unloading the header. The original motivation to keep
> > trace_printk.h in kernel.h was just because a similar printk.h is living
> > there. But after all, this is a purely debugging header, so no need for
> > almost every C file to bear debugging stuff.  
> 
> It is a big deal for debugging stuff. A lot of developers debug their code
> with trace_printk(), and do the "shotgun approach", where they cut and
> paste trace_printk()s all over their code in several files. Having to now add:
> 
>   #include <linux/trace_printk.h>
> 
> whenever a trace_printk() is added is going to be a big PITA and slow down
> all debugging efforts.
>

I don't actually remember why I had __trace_puts() pass in the size. I
could change it to:

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5b46924fdff5..d5a939b8c391 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -331,10 +331,10 @@ int __trace_printk(unsigned long ip, const char *fmt, ...);
 	if (__builtin_constant_p(str))					\
 		__trace_bputs(_THIS_IP_, trace_printk_fmt);		\
 	else								\
-		__trace_puts(_THIS_IP_, str, strlen(str));		\
+		__trace_puts(_THIS_IP_, str);				\
 })
 extern int __trace_bputs(unsigned long ip, const char *str);
-extern int __trace_puts(unsigned long ip, const char *str, int size);
+extern int __trace_puts(unsigned long ip, const char *str);

 extern void trace_dump_stack(int skip);

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e575956ef9b5..686741edb803 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1178,11 +1178,10 @@ EXPORT_SYMBOL_GPL(__trace_array_puts);
  * __trace_puts - write a constant string into the trace buffer.
  * @ip:	   The address of the caller
  * @str:   The constant string to write
- * @size:  The size of the string.
  */
-int __trace_puts(unsigned long ip, const char *str, int size)
+int __trace_puts(unsigned long ip, const char *str)
 {
-	return __trace_array_puts(printk_trace, ip, str, size);
+	return __trace_array_puts(printk_trace, ip, str, strlen(str));
 }
 EXPORT_SYMBOL_GPL(__trace_puts);

@@ -1201,7 +1200,7 @@ int __trace_bputs(unsigned long ip, const char *str)
 	int size = sizeof(struct bputs_entry);

 	if (!printk_binsafe(tr))
-		return __trace_puts(ip, str, strlen(str));
+		return __trace_puts(ip, str);

 	if (!(tr->trace_flags & TRACE_ITER(PRINTK)))
 		return 0;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b6d42fe06115..de4e6713b84e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -2116,7 +2116,7 @@ extern void tracing_log_err(struct trace_array *tr,
  * about performance). The internal_trace_puts() is for such
  * a purpose.
  */
-#define internal_trace_puts(str) __trace_puts(_THIS_IP_, str, strlen(str))
+#define internal_trace_puts(str) __trace_puts(_THIS_IP_, str)

 #undef FTRACE_ENTRY
 #define FTRACE_ENTRY(call, struct_name, id, tstruct, print)	\

Which removes the strlen() altogether.

-- Steve