From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F2183382391; Mon, 30 Mar 2026 18:35:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774895722; cv=none; b=ERH0Z2pq1sOn6vSzUz36Tpj03IMyG4To2frg1+Qx0zIpRSmilFm2UgiVsZB0NhfTWC5dstD1ZEfzODxb6X63l+zhys/pg7o3AtoGRKkrmfFYEphcOdRFvUrgfM5wI3AGvhzccl+WNu3towW+IjHf+O8knyF6Xtm0fslJV2dvRd8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774895722; c=relaxed/simple; bh=EOqj3nBvuQfsTeUDP+okcSbKnOSzy+P47F21/QpVQg0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=C3ic86yJ1alyS19plORo3NV1S+hZ1u+b5Ya+8Rp3ZeJpN7nvHpS2aK2yoxC/L9nuylm+42HCZFXDsEXR8p2d3nipglYgtSeThnj3zGqRv3Uvw5UynAYhketaxlfEuGHuc14p2Ws+r6foxM6+d80kZALSui+13wX8CvUC8dTbj5U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id B6C868C58F; Mon, 30 Mar 2026 18:35:19 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf12.hostedemail.com (Postfix) with ESMTPA id C7F1826; Mon, 30 Mar 2026 18:35:17 +0000 (UTC) Date: Mon, 30 Mar 2026 14:36:13 -0400 From: Steven Rostedt To: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Ian Rogers Subject: Re: [PATCH v14 4/5] ring-buffer: Reset RB_MISSED_* flags on persistent ring buffer Message-ID: <20260330143613.42fe5640@gandalf.local.home> In-Reply-To: <177487501981.3463592.2886576368556755178.stgit@mhiramat.tok.corp.google.com> References: <177487498530.3463592.12715592581212799257.stgit@mhiramat.tok.corp.google.com> <177487501981.3463592.2886576368556755178.stgit@mhiramat.tok.corp.google.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout05 X-Rspamd-Queue-Id: C7F1826 X-Stat-Signature: 55upi39x8omt961at3c3qge51q5ucp4p X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18LxE9r6BJ+WZx2D88s9R35zeAlDnm4jsk= X-HE-Tag: 1774895717-370769 X-HE-Meta: U2FsdGVkX1/mtvWvVBZREd6O2hoWI6Hr6T/WbgeF3dHah5VJ8D5MnHNnORMM6hdeHxJpi+KdpsdtwjimIK4lJK1WxrN035qHIqquQagin9SjTe7hFQn12GnEX5TJCAyf+b7keg5L4FxQzWGsmyPyxntxJAMIFSiG2xuUTqEkvvQ9hFQknu/1OKE3wqYls/qJFCZdgQsuCy9vwsfBo5/OOvTqkGjSkGAYzi8EyknmKR+krEUdXIT8elenORxpfE7vzGp51gis78ZamQKska3E2uEWRUGbTbKKPWlhEfLNktsV+UFhXkzVpa/nogRsh/aVlmIGoSgRs8hjSDee2SvSQ4wqeOqo0uHr On Mon, 30 Mar 2026 21:50:20 +0900 "Masami Hiramatsu (Google)" wrote: > From: Masami Hiramatsu (Google) > > Reset RB_MISSED_* flags when the persistent ring buffer is > validated at boot. Since these flags are used only in reading > process, such process should be stopped when reboot and never > be restarted. Thus, these flags are meaningless in the next > boot. Moreover, it can confuse the read process after reboot. Is it meaningless on a second boot? Let's say you have a crash, and there's an invalid buffer. On the next boot it is flagged as invalid with the RB_MISSED flag. But then you reboot again before looking at the buffer. The next boot will clear this flag. Now looking at the persistent ring buffer will not show any missed events. Ideally, it shouldn't matter how many reboots are made. If the persistent ring buffer hasn't started again, it should always show the same output. -- Steve > > Signed-off-by: Masami Hiramatsu (Google) > --- > Changes in v14: > - Newly added. > --- > kernel/trace/ring_buffer.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index e5178239f2f9..5049cf13021e 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1903,6 +1903,7 @@ static int rb_validate_buffer(struct buffer_page *bpage, int cpu, > local_set(&bpage->page->commit, 0); > } else { > local_set(&bpage->entries, ret); > + local_set(&bpage->page->commit, tail); > } > > return ret;