Merge tag 'trace-ringbuffer-v7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

7acfa2c5 · Linus Torvalds <[email protected]> · 2026-05-21 14:05:09 -07:00

Pull ring-buffer fixes from Steven Rostedt:

 - Fix reporting MISSED EVENTS in trace iterator

   When the "trace" file is read with tracing enabled, if the writer
   were to pass the iterator reader, it resets, sets a "missed_events"
   flag and continues. The tracing output checks for missed events and
   if there are some, it prints out "[LOST EVENTS]" to let the user know
   events were dropped.

   But the clearing of the missed_events happened when the tracing
   system queried the ring buffer iterator about missed events. This was
   premature as the ring buffer is per CPU, and the tracing code reads
   all the CPU buffers and checks for missed events when it is read. If
   the CPU iterator that had missed events isn't printed next, the
   output for the LOST EVENTS is lost.

   Clear the missed_events flag when the iterator moves to the next
   event and not when the missed_events flag is queried. Also clear it
   on reset.

 - Flush and stop the persistent ring buffer on panic

   On panic the persistent ring buffer is used to debug what caused the
   panic. But on some architectures, it requires flushing the memory
   from cache, otherwise, the ring buffer persistent memory may not have
   the last events and this could also cause the ring buffer to be
   corrupted on the next boot.

 - Fix nr_subbufs initialization in simple_ring_buffer_init_mm

   The remote simple ring buffer meta data nr_subbufs is initialized too
   early and gets cleared later on, making it zero and not reflect the
   actual number of sub-buffers.

 - Fix unload_page for simple_ring_buffer init rollback

   On error, the pages loaded need to be unloaded. To unload a page it
   is expected that: page = load_page(va); -> unload_page(page). But the
   code was doing: unload_page(va) and not unload_page(page).

 - Create output file from cmd_check_undefined

   The check for undefined symbols checks if the file *.o.checked exists
   and if so it skips doing the work. But the *.o.checked file never was
   created making every build do the work even when it was already done
   previously.

* tag 'trace-ringbuffer-v7.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Create output file from cmd_check_undefined
  tracing: Fix unload_page for simple_ring_buffer init rollback
  tracing: Fix nr_subbufs initialization in simple_ring_buffer_init_mm()
  ring-buffer: Flush and stop persistent ring buffer on panic
  ring-buffer: Fix reporting of missed events in iterator

Commit

7acfa2c5f4366d63653380646ffa7dbd1bfaccc0

Parents

758c807b · 057caace

Merge commit. Changes below are compared with the first parent: 758c807b.

Changes

25 files changed · +72 −8