linux-kernel - Re: [for-next][PATCH 0/3] tracing: Trigger a warning on build if a tracepoint is defined but unused

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Message-ID: <20250829070224.503ddc8a@canb.auug.org.au>
Date: Fri, 29 Aug 2025 07:02:24 +1000
From: Stephen Rothwell <sfr@...b.auug.org.au>
To: Steven Rostedt <rostedt@...nel.org>
Cc: linux-kernel@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [for-next][PATCH 0/3] tracing: Trigger a warning on build if a
 tracepoint is defined but unused

Hi Steven,

On Thu, 28 Aug 2025 14:27:54 -0400 Steven Rostedt <rostedt@...nel.org> wrote:
>
> I built this against all archs in my tree (26 of them) with a allyesconfig.
> Unfortunately, only 10 build successfully with that (they all build
> successfully with defconfig and this option with tracing enabled). This
> detected 178 unique tracepoints that are defined and not used:
> 
> $ grep '^warning:' /work/autotest/cross-unused-traceevnts.log | sort -u |wc -l
> 178
> 
> Among them, 78 tracepoints were created and never referenced.
> 
> $ grep '^warning:' /work/autotest/cross-unused-traceevents.log | sort -u |cut -d"'" -f2 |
>     while read a ; do if ! git grep -q trace_$a ; then echo $a; fi ; done | wc -l
> 78
> 
> The 100 remaining are likely in strange #ifdef CONFIG combinations where an
> allyesconfig defines the tracepoint but doesn't enable the code that uses
> them.

[Pretending to be Linus :-)]

So, have you fixed up the 178 new warnings you know about?  I cannot
possibly do that, or even notify the offenders.  Please do that before
adding this code to linux-next.

But, really, these known warnings can just make it so much harder to
notice new ones.
-- 
Cheers,
Stephen Rothwell

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