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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4234C433FE for ; Sun, 24 Oct 2021 22:56:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC11760FE7 for ; Sun, 24 Oct 2021 22:56:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231961AbhJXW7E (ORCPT ); Sun, 24 Oct 2021 18:59:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:34140 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229625AbhJXW7D (ORCPT ); Sun, 24 Oct 2021 18:59:03 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C9ECB60F70; Sun, 24 Oct 2021 22:56:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1635116201; bh=rYMQ5XtMn1HanoUiiZbbivTpo2vmneWSjyU+LSj6QkQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=s/Daia3dR3CsbCcCsscr25qy6+731kQijgRBryxbo9I7wqzeLu8KTT6vr5V8DkFI5 s+ro+s6MfEfTSXXYOdK9ZwFH9QGeDA9AEHBwfXnHU2t+n5IP/lH//XXyRB02ebux0x eVfWKn96wGwhBxlfYOX+VqRYkrRbk9bwejPkrJFQrjHYPQXc1m5PsgM2PoVftVXYSo iaVky3uKcJ7qhEsTez/qgn+LUvyPVaBI761e30Xonh4nXkiFP/9zanK3ARGCpeOvHL 0b0DaV3ilw56YQkRQ6fiZpl6dgTcigmuTl2avZ9NW2u58QiTj01z/yhHto0JuKdbTp tRTIdmIQjIPPg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 46F865C0BF4; Sun, 24 Oct 2021 15:56:40 -0700 (PDT) Date: Sun, 24 Oct 2021 15:56:40 -0700 From: "Paul E. McKenney" To: "Li, Zhijian" Cc: dave@stgolabs.net, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Philip Li , kernel test robot Subject: Re: [PATCH 2/2] refscale: prevent buffer to pr_alert() being too long Message-ID: <20211024225640.GL880162@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20211022105111.29455-1-lizhijian@cn.fujitsu.com> <20211022105111.29455-2-lizhijian@cn.fujitsu.com> <20211022231555.GG880162@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 24, 2021 at 10:46:16PM +0800, Li, Zhijian wrote: > > on 2021/10/23 7:15, Paul E. McKenney wrote: > > On Fri, Oct 22, 2021 at 06:51:11PM +0800, Li Zhijian wrote: > > > 0Day/LKP observed that the refscale results become incompleted > > > when a larger nruns(such as 300) is specified. > > > It seems that printk() can accept < 1024 buffer at once. > > > Print the buffer if its length exceeds 800 simply. > > > > > > CC: Philip Li > > > Reported-by: kernel test robot > > > Signed-off-by: Li Zhijian > > Good catch! A couple of questions below. > > > > Thanx, Paul > > > > > --- > > > kernel/rcu/refscale.c | 23 +++++++++++++---------- > > > 1 file changed, 13 insertions(+), 10 deletions(-) > > > > > > diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c > > > index 2cbe2a2ba387..b1b9052010fd 100644 > > > --- a/kernel/rcu/refscale.c > > > +++ b/kernel/rcu/refscale.c > > > @@ -604,7 +604,7 @@ static u64 process_durations(int n) > > > char *buf; > > > u64 sum = 0; > > > - buf = kmalloc(128 + nreaders * 32, GFP_KERNEL); > > > + buf = kmalloc(64 * 20, GFP_KERNEL); > > This allocation (and the one below) is 1280 bytes rather than > > 1024 bytes. Why the extra couple hundred bytes? > > Nothing special, so let's change 1024 or (800 + 64 ),which is sufficent as well ? Either works. No problem having a few extra bytes, but 200 seemed a bit excessive. ;-) > > > if (!buf) > > > return 0; > > > buf[0] = 0; > > > @@ -617,13 +617,15 @@ static u64 process_durations(int n) > > > if (i % 5 == 0) > > > strcat(buf, "\n"); > > > + if (strlen(buf) > 800) { > > > + pr_alert("%s", buf); > > Does the tools/testing/selftests/rcutorture/bin/kvm-recheck-refscale.sh > > script also require changes to handle the partial lines? > > I missed that, i will take a look at it Looking forward to seeing what you come up with. Thanx, Paul > Thanks > > Zhijian > > > > > > Same for the later comparison against 800. > > > > > + buf[0] = 0; > > > + } > > > strcat(buf, buf1); > > > sum += rt->last_duration_ns; > > > } > > > - strcat(buf, "\n"); > > > - > > > - SCALEOUT("%s\n", buf); > > > + pr_alert("%s\n", buf); > > > kfree(buf); > > > return sum; > > > @@ -648,7 +650,7 @@ static int main_func(void *arg) > > > VERBOSE_SCALEOUT("main_func task started"); > > > result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL); > > > - buf = kzalloc(64 + nruns * 32, GFP_KERNEL); > > > + buf = kzalloc(64 * 20, GFP_KERNEL); > > > if (!result_avg || !buf) { > > > VERBOSE_SCALEOUT_ERRSTRING("out of memory"); > > > errexit = true; > > > @@ -701,10 +703,7 @@ static int main_func(void *arg) > > > if (errexit) > > > goto err; > > > - buf[0] = 0; > > > - strcat(buf, "\n"); > > > - strcat(buf, "Runs\tTime(ns)\n"); > > > - > > > + pr_alert("Runs\tTime(ns)\n"); > > > for (exp = 0; exp < nruns; exp++) { > > > u64 avg; > > > u32 rem; > > > @@ -712,9 +711,13 @@ static int main_func(void *arg) > > > avg = div_u64_rem(result_avg[exp], 1000, &rem); > > > sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem); > > > strcat(buf, buf1); > > > + if (strlen(buf) > 800) { > > > + pr_alert("%s", buf); > > > + buf[0] = 0; > > > + } > > > } > > > - SCALEOUT("%s", buf); > > > + pr_alert("%s", buf); > > > err: > > > // This will shutdown everything including us. > > > -- > > > 2.33.0 > > > > > > > > > > > > >