linux-kernel - Re: [PATCH v2 0/5] ftrace: Fix fprobe with function graph accounting

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Message-ID: <20250220115258.7558Aa9-hca@linux.ibm.com>
Date: Thu, 20 Feb 2025 12:52:58 +0100
From: Heiko Carstens <hca@...ux.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-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>,
        Sven Schnelle <svens@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>
Subject: Re: [PATCH v2 0/5] ftrace: Fix fprobe with function graph accounting

On Wed, Feb 19, 2025 at 05:04:36PM -0500, Steven Rostedt wrote:
> Heiko Carstens reported[1] a bug when running the ftrace selftests.
> After running them, he noticed that the enabled_functions file had
> all functions enabled in it. That means something was registered to
> ftrace that shouldn't be.
> 
> The issue was with the accounting of the new fprobe logic which was
> built on top of the function graph infrastructure. Patch 3 of this
> series is the fix for that bug, but while debugging that, 3 other
> accounting bugs were discovered.
...
> Steven Rostedt (5):
>       ftrace: Fix accounting of adding subops to a manager ops
>       ftrace: Do not add duplicate entries in subops manager ops
>       fprobe: Always unregister fgraph function from ops
>       fprobe: Fix accounting of when to unregister from function graph
>       selftests/ftrace: Update fprobe test to check enabled_functions file
> 
> ----
>  kernel/trace/fprobe.c                              | 12 ++---
>  kernel/trace/ftrace.c                              | 33 +++++++++----
>  .../ftrace/test.d/dynevent/add_remove_fprobe.tc    | 54 ++++++++++++++++++++++
>  3 files changed, 82 insertions(+), 17 deletions(-)

FWIW, I can confirm that this fixes the bug I reported.
Feel free to add

Tested-by: Heiko Carstens <hca@...ux.ibm.com>