Re: [PATCH v2 2/4] ring-buffer: Flush and stop persistent ring buffer on panic

On Wed, 18 Feb 2026 19:14:28 +0900
"Masami Hiramatsu (Google)" [off-list ref] wrote:

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

On a real hardware, since panic and reboot the machine will not
flush hardware cache to the persistent ring buffer, the events
written right before the panic can be lost. Moreover, since
there will be an inconsistency between the commit counter (which
is written atomically via local_set()) and the data, validation
will fail and all data in the persistent ring buffer will be lost.

Here's a bit of a fix up on the text:

   On real hardware, panic and machine reboot may not flush hardware cache
   to memory. This means the persistent ring buffer, which relies on a
   coherent state of memory, may not have its events written to the buffer
   and they may be lost. Moreover, there may be inconsistency with the
   counters which are used for validation of the integrity of the
   persistent ring buffer which may cause all data to be discarded.

To avoid this issue, this will stop recording on the ring buffer
and flush cache at the reserved memory on panic.

   To avoid this issue, stop recording of the ring buffer on panic and
   flush the cache of the ring buffer's memory.


-- Steve