From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1EA2830DD2F; Tue, 31 Mar 2026 01:43:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774921398; cv=none; b=cgnrllCO4G7WFwlXcZ+lx6dal+k8TAEv7oAaucn8zj07FYB+RSvM3i7m0/Yu44HSbDbDcMVe5dpiHvOz0wZ5W40VAEYbGeocgGcV63X2cceDDN7mcGcJpd49fqoEDHq8WdO4qid4ScpLbDIY6ygTJ1kTcCBiVwx8pBrtJl9IRE0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774921398; c=relaxed/simple; bh=DkKghEXTvkuoAUKnz/L6+CM+9iswGKKMeh3dCg+qPMw=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=jKPxuqJo8y3Tb4KRGsrMOoDyvDWTHaJzi+8+W5P7gVPS0wgb6fesVhQ0/8KsdJAnc3BA7Q0FkH8UKzkRyB4iIRdIHFry1YtZAzGds+tlcl9oiyRnIcEVPHfx+QmrOb+IExCFhjq3UQCw72f9dzi6/Xd+azF2quK32gUmARwrkLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rfQndXYb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rfQndXYb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F028CC4CEF7; Tue, 31 Mar 2026 01:43:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774921397; bh=DkKghEXTvkuoAUKnz/L6+CM+9iswGKKMeh3dCg+qPMw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rfQndXYbNrtaV6Ec+MhpRqFN/I/okFI2Yr2wLoNwUCd2XQiza/hnSo/sRXqJjQwc5 AUuAUPqZA0LHpJNCAU7jD1lj1SazwgAhGVyXvqr1wb3vmoWYN9YziuNaZuM/eJLXjR bmmhk82+Dr03uBnTI9xCJF2Ug+Mm1dox3HFiyFS2/xuuTOnSQqipl5xKcyWXvzKcZY IIvp1DSrsyec3puGpbKsKApIstYDOiGNR8G/ToZq6VRBfhpcRrud9lJn1k8TTO/Oik X2tV8SvO68C+UqRDlsRm7a3f5dwM8GJL+EWJkLQ6UVXMdzNk6eSDa25xaPZwAdefxl Mpdc8ztC64D9w== Date: Tue, 31 Mar 2026 10:43:15 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt 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: <20260331104315.708238643b1aa257e642a07b@kernel.org> In-Reply-To: <20260330143613.42fe5640@gandalf.local.home> References: <177487498530.3463592.12715592581212799257.stgit@mhiramat.tok.corp.google.com> <177487501981.3463592.2886576368556755178.stgit@mhiramat.tok.corp.google.com> <20260330143613.42fe5640@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (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 On Mon, 30 Mar 2026 14:36:13 -0400 Steven Rostedt wrote: > 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. Hmm, OK. I'll drop this. Thanks! > > -- 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; > > -- Masami Hiramatsu (Google)