linux-kernel - Re: [PATCH v6 0/4] tracing: Remove backup instance after read all

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Message-Id: <20260205094142.03d87e2d482649cb51355017@kernel.org>
Date: Thu, 5 Feb 2026 09:41:42 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/4] tracing: Remove backup instance after read all

Hi Steve,

Can you review this series?

On Sun,  1 Feb 2026 12:28:55 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> Hi,
> 
> Here is the v6 of the series to improve backup instances of
> the persistent ring buffer. The previous version is here:
> 
> https://lore.kernel.org/all/176955897718.2786091.11948759407196200082.stgit@mhiramat.tok.corp.google.com/
> 
> This version cleanup code and fix typo, according to Steve's
> comments. Also fix to init autoremove_wq only when the readonly
> instance has been made. A major UI change is that the tracing_on
> file is also removed from readonly instance.
> 
> Since backup instances are a kind of snapshot of the persistent
> ring buffer, it should be readonly. And if it is readonly
> there is no reason to keep it after reading all data via trace_pipe
> because the data has been consumed. But user should be able to remove
> the readonly instance by rmdir or truncating `trace` file.
> 
> Thus, [2/4] makes backup instances readonly (not able to write any
> events, cleanup trace, change buffer size). Also, [3/4] removes the
> backup instance after consuming all data via trace_pipe.
> With this improvements, even if we makes a backup instance (using
> the same amount of memory of the persistent ring buffer), it will
> be removed after reading the data automatically.
> 
> ---
> 
> Masami Hiramatsu (Google) (4):
>       tracing: Reset last_boot_info if ring buffer is reset
>       tracing: Make the backup instance non-reusable
>       tracing: Remove the backup instance automatically after read
>       tracing/Documentation: Add a section about backup instance
> 
> 
>  Documentation/trace/debugging.rst |   19 ++++
>  kernel/trace/trace.c              |  162 ++++++++++++++++++++++++++++++-------
>  kernel/trace/trace.h              |   13 +++
>  kernel/trace/trace_boot.c         |    5 +
>  kernel/trace/trace_events.c       |   76 ++++++++++-------
>  5 files changed, 209 insertions(+), 66 deletions(-)
> 
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>