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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 BB75EC3279B for ; Mon, 2 Jul 2018 09:23:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 772EC20849 for ; Mon, 2 Jul 2018 09:23:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 772EC20849 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933907AbeGBJXi convert rfc822-to-8bit (ORCPT ); Mon, 2 Jul 2018 05:23:38 -0400 Received: from smtp-out6.electric.net ([192.162.217.185]:63645 "EHLO smtp-out6.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933829AbeGBJXe (ORCPT ); Mon, 2 Jul 2018 05:23:34 -0400 Received: from 1fZv3T-0000gQ-Uu by out6a.electric.net with emc1-ok (Exim 4.90_1) (envelope-from ) id 1fZv3U-0000my-VJ; Mon, 02 Jul 2018 02:23:32 -0700 Received: by emcmailer; Mon, 02 Jul 2018 02:23:32 -0700 Received: from [156.67.243.126] (helo=AcuMS.aculab.com) by out6a.electric.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1fZv3T-0000gQ-Uu; Mon, 02 Jul 2018 02:23:31 -0700 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 2 Jul 2018 10:25:11 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 2 Jul 2018 10:25:11 +0100 From: David Laight To: 'Taeung Song' , Alexei Starovoitov , Daniel Borkmann CC: Teng Qin , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH 3/4] samples/bpf: Check the error of write() and read() Thread-Topic: [PATCH 3/4] samples/bpf: Check the error of write() and read() Thread-Index: AQHUEeXT5Bh7AKk1jEeTWRWtKGH1caR7qFeA Date: Mon, 2 Jul 2018 09:25:11 +0000 Message-ID: References: <1530522893-8961-1-git-send-email-treeze.taeung@gmail.com> <1530522893-8961-4-git-send-email-treeze.taeung@gmail.com> In-Reply-To: <1530522893-8961-4-git-send-email-treeze.taeung@gmail.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.33] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Outbound-IP: 156.67.243.126 X-Env-From: David.Laight@ACULAB.COM X-Proto: esmtps X-Revdns: X-HELO: AcuMS.aculab.com X-TLS: TLSv1.2:ECDHE-RSA-AES256-SHA384:256 X-Authenticated_ID: X-PolicySMART: 3396946, 3397078 X-Virus-Status: Scanned by VirusSMART (c) X-Virus-Status: Scanned by VirusSMART (s) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Taeung Song > Sent: 02 July 2018 10:15 > test_task_rename() and test_urandom_read() > can be failed during write() and read(), > So check the result of them. > > Signed-off-by: Taeung Song > --- > samples/bpf/test_overhead_user.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/samples/bpf/test_overhead_user.c b/samples/bpf/test_overhead_user.c > index 6caf47a..8a88d9c 100644 > --- a/samples/bpf/test_overhead_user.c > +++ b/samples/bpf/test_overhead_user.c > @@ -6,6 +6,7 @@ > */ > #define _GNU_SOURCE > #include > +#include > #include > #include > #include > @@ -44,8 +45,12 @@ static void test_task_rename(int cpu) > exit(1); > } > start_time = time_get_ns(); > - for (i = 0; i < MAX_CNT; i++) > - write(fd, buf, sizeof(buf)); > + for (i = 0; i < MAX_CNT; i++) { > + if (write(fd, buf, sizeof(buf)) < 0) { > + printf("task rename failed: %s\n", strerror(errno)); > + break; I'm not sure 'break' generates sensible output. > + } > + } What about partial writes?? > printf("task_rename:%d: %lld events per sec\n", > cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time)); > close(fd); > @@ -55,7 +60,7 @@ static void test_urandom_read(int cpu) > { > __u64 start_time; > char buf[4]; > - int i, fd; > + int i, fd, err = 0; > > fd = open("/dev/urandom", O_RDONLY); > if (fd < 0) { > @@ -63,8 +68,13 @@ static void test_urandom_read(int cpu) > exit(1); > } > start_time = time_get_ns(); > - for (i = 0; i < MAX_CNT; i++) > - read(fd, buf, sizeof(buf)); > + for (i = 0; i < MAX_CNT; i++) { > + err = read(fd, buf, sizeof(buf)); > + if (err < 0 || err >= sizeof(buf)) { Overlong reads indicate that something is seriously awry. Short reads are valid - but maybe not expected. > + printf("failed to read from /dev/urandom: %s\n", strerror(errno)); strerror() won't give anything sensible unless err == -1; You probably want to include the loop count. > + break; The summary print will be gibberish after break. > + } > + } > printf("urandom_read:%d: %lld events per sec\n", > cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time)); > close(fd); > -- > 2.7.4