From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FA48C5ACD6 for ; Tue, 17 Mar 2020 21:35:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D70CD20738 for ; Tue, 17 Mar 2020 21:35:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727103AbgCQVfJ (ORCPT ); Tue, 17 Mar 2020 17:35:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:53630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727340AbgCQVeS (ORCPT ); Tue, 17 Mar 2020 17:34:18 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 590E820789; Tue, 17 Mar 2020 21:34:17 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1jEJqq-000EX8-9C; Tue, 17 Mar 2020 17:34:16 -0400 Message-Id: <20200317213416.163549674@goodmis.org> User-Agent: quilt/0.65 Date: Tue, 17 Mar 2020 17:32:26 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Peter Zijlstra , Masami Hiramatsu , Alexei Starovoitov , Peter Wu , Jonathan Corbet , Tom Zanussi Subject: [RFC][PATCH 04/11] ring-buffer: Add page_stamp to iterator for synchronization References: <20200317213222.421100128@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" Have the ring_buffer_iter structure contain a page_stamp, such that it can be used to see if the writer entered the page the iterator is on. When going to a new page, the iterator will record the time stamp of that page. When reading events, it can copy the event to an internal buffer on the iterator (to be implemented later), then check the page's time stamp with its own to see if the writer entered the page. If so, it will need to try to read the event again. Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ring_buffer.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index f57eeaa80e3e..e689bdcb53e8 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -507,6 +507,7 @@ struct ring_buffer_iter { struct buffer_page *cache_reader_page; unsigned long cache_read; u64 read_stamp; + u64 page_stamp; }; /** @@ -1959,7 +1960,7 @@ static void rb_inc_iter(struct ring_buffer_iter *iter) else rb_inc_page(cpu_buffer, &iter->head_page); - iter->read_stamp = iter->head_page->page->time_stamp; + iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; } @@ -3551,10 +3552,13 @@ static void rb_iter_reset(struct ring_buffer_iter *iter) iter->cache_reader_page = iter->head_page; iter->cache_read = cpu_buffer->read; - if (iter->head) + if (iter->head) { iter->read_stamp = cpu_buffer->read_stamp; - else + iter->page_stamp = cpu_buffer->reader_page->page->time_stamp; + } else { iter->read_stamp = iter->head_page->page->time_stamp; + iter->page_stamp = iter->read_stamp; + } } /** -- 2.25.1