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32dc004252
Reset the last-boot ring buffers when read() reads out all cpu buffers through trace_pipe/trace_pipe_raw. This prevents ftrace to unwind ring buffer read pointer next boot. Note that this resets only when all per-cpu buffers are empty, and read via read(2) syscall. For example, if you read only one of the per-cpu trace_pipe, it does not reset it. Also, reading buffer by splice(2) syscall does not reset because some data in the reader (the last) page. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/174792929202.496143.8184644221859580999.stgit@mhiramat.tok.corp.google.com Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>