linux-kernel - Re: [PATCH v3 0/2] tracing: Remove backup instance after read all

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Message-Id: <20260120002740.7962e180f9ea88006a32abb9@kernel.org>
Date: Tue, 20 Jan 2026 00:27:40 +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 v3 0/2] tracing: Remove backup instance after read all

I found another bug on this (or persistent ring buffer itself)
Let me fix it first.

On Tue, 13 Jan 2026 15:52:13 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> Hi,
> 
> Here is the 3rd version of the series to improve backup instances of
> the persistent ring buffer. The previous version is here:
> 
> https://lore.kernel.org/all/176788217131.1398317.11144318616426272901.stgit@mhiramat.tok.corp.google.com/
> 
> In this version, I updated [1/2] to back to checking readonly
> flag and consolidate the eventfs_entries.
> 
> 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.
> Thus, [1/2] makes backup instances readonly (not able to write any
> events, cleanup trace, change buffer size). Also, [2/2] 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) (2):
>       tracing: Make the backup instance readonly
>       tracing: Add autoremove feature to the backup instance
> 
> 
>  kernel/trace/trace.c        |  164 +++++++++++++++++++++++++++++++++++--------
>  kernel/trace/trace.h        |   14 +++-
>  kernel/trace/trace_boot.c   |    5 +
>  kernel/trace/trace_events.c |   68 +++++++++++-------
>  4 files changed, 191 insertions(+), 60 deletions(-)
> 
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>


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