linux-kernel - Re: [PATCH] scripts/decode_stacktrace.sh: fix build ID and PC source parsing

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Message-Id: <20251030205758.b3a4de16bc8ce7ca90383f86@linux-foundation.org>
Date: Thu, 30 Oct 2025 20:57:58 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Carlos Llamas <cmllamas@...gle.com>
Cc: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, Breno Leitao
 <leitao@...ian.org>, Luca Ceresoli <luca.ceresoli@...tlin.com>, Miroslav
 Benes <mbenes@...e.cz>, Mark Brown <broonie@...nel.org>, Puranjay Mohan
 <puranjay@...nel.org>, Mark Rutland <mark.rutland@....com>, Catalin Marinas
 <catalin.marinas@....com>, kernel-team@...roid.com,
 linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] scripts/decode_stacktrace.sh: fix build ID and PC
 source parsing

On Thu, 30 Oct 2025 01:03:33 +0000 Carlos Llamas <cmllamas@...gle.com> wrote:

> Support for parsing PC source info in stacktraces (e.g. '(P)') was
> added in commit 2bff77c665ed ("scripts/decode_stacktrace.sh: fix
> decoding of lines with an additional info"). However, this logic was
> placed after the build ID processing. This incorrect order fails to
> parse lines containing both elements, e.g.:
> 
>   drm_gem_mmap_obj+0x114/0x200 [drm 03d0564e0529947d67bb2008c3548be77279fd27] (P)
> 
> This patch fixes the problem by extracting the PC source info first and
> then processing the module build ID. With this change, the line above is
> now properly parsed as such:
> 
>   drm_gem_mmap_obj (./include/linux/mmap_lock.h:212 ./include/linux/mm.h:811 drivers/gpu/drm/drm_gem.c:1177) drm (P)
> 
> While here, also add a brief explanation the build ID section.

Thanks for fixing this.  I'll queue it in mm.git's mm-hotfixes branch
with a plan to upstream it into 6.18-rcX.

I'll add a cc:stable tag so this gets fixed in earlier kernel releases
also.

But....

> Fixes: bdf8eafbf7f5 ("arm64: stacktrace: report source of unwind data")
> Fixes: 2bff77c665ed ("scripts/decode_stacktrace.sh: fix decoding of lines with an additional info")

Which kernel releases?  We're fixing a commit from Oct 2024 and a
commit from Jan 2025.  How are downstream people to understand what
we're recommending here?

I view the Fixes: as a recommendation we make to -stable maintainers
saying "I think this should be backported to <here> and later".  As
such, giving them multiple backporting targets must make their little
heads spin.

So can we choose a single point in KernelTime here?  And reflect this
in a single Fixes: line?

Thanks.

Joe, I'd appreciate it if checkpatch weer to somehow draw people's
attention to this (fairly frequent) problem.