From: Steven Rostedt <rostedt@xxxxxxxxxxx> commit 97937834ae876f29565415ab15f1284666dc6be3 upstream. The pages_touched field represents the number of subbuffers in the ring buffer that have content that can be read. This is used in accounting of "dirty_pages" and "buffer_percent" to allow the user to wait for the buffer to be filled to a certain amount before it reads the buffer in blocking mode. The persistent buffer never updated this value so it was set to zero, and this accounting would take it as it had no content. This would cause user space to wait for content even though there's enough content in the ring buffer that satisfies the buffer_percent. Cc: stable@xxxxxxxxxxxxxxx Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Vincent Donnefort <vdonnefort@xxxxxxxxxx> Link: https://lore.kernel.org/20250214123512.0631436e@xxxxxxxxxxxxxxxxxx Fixes: 5f3b6e839f3ce ("ring-buffer: Validate boot range memory events") Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/trace/ring_buffer.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1850,6 +1850,11 @@ static void rb_meta_validate_events(stru cpu_buffer->cpu); goto invalid; } + + /* If the buffer has content, update pages_touched */ + if (ret) + local_inc(&cpu_buffer->pages_touched); + entries += ret; entry_bytes += local_read(&head_page->page->commit); local_set(&cpu_buffer->head_page->entries, ret); Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are queue-6.12/ring-buffer-update-pages_touched-to-reflect-persistent-buffer-content.patch queue-6.12/ring-buffer-unlock-resize-on-mmap-error.patch queue-6.12/rtla-timerlat_hist-abort-event-processing-on-second-.patch queue-6.12/rtla-timerlat_top-abort-event-processing-on-second-s.patch queue-6.12/tracing-do-not-allow-mmap-of-persistent-ring-buffer.patch queue-6.12/ring-buffer-validate-the-persistent-meta-data-subbuf-array.patch
