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)" [off-list ref] 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/ (local)

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) [off-list ref]

-- 
Masami Hiramatsu (Google) [off-list ref]