From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:57062 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932851AbeFRIZz (ORCPT ); Mon, 18 Jun 2018 04:25:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yury Norov , Andrew Morton , Fengguang Wu , Linus Torvalds , Sasha Levin Subject: [PATCH 4.16 227/279] lib/find_bit_benchmark.c: avoid soft lockup in test_find_first_bit() Date: Mon, 18 Jun 2018 10:13:32 +0200 Message-Id: <20180618080618.216781441@linuxfoundation.org> In-Reply-To: <20180618080608.851973560@linuxfoundation.org> References: <20180618080608.851973560@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yury Norov [ Upstream commit 4ba281d5bd9907355e6b79fb72049c9ed50cc670 ] test_find_first_bit() is intentionally sub-optimal, and may cause soft lockup due to long time of run on some systems. So decrease length of bitmap to traverse to avoid lockup. With the change below, time of test execution doesn't exceed 0.2 seconds on my testing system. Link: http://lkml.kernel.org/r/20180420171949.15710-1-ynorov@caviumnetworks.com Fixes: 4441fca0a27f5 ("lib: test module for find_*_bit() functions") Signed-off-by: Yury Norov Reviewed-by: Andrew Morton Reported-by: Fengguang Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- lib/find_bit_benchmark.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/lib/find_bit_benchmark.c +++ b/lib/find_bit_benchmark.c @@ -132,7 +132,12 @@ static int __init find_bit_test(void) test_find_next_bit(bitmap, BITMAP_LEN); test_find_next_zero_bit(bitmap, BITMAP_LEN); test_find_last_bit(bitmap, BITMAP_LEN); - test_find_first_bit(bitmap, BITMAP_LEN); + + /* + * test_find_first_bit() may take some time, so + * traverse only part of bitmap to avoid soft lockup. + */ + test_find_first_bit(bitmap, BITMAP_LEN / 10); test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); pr_err("\nStart testing find_bit() with sparse bitmap\n");