From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:59496 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388731AbeIXSpl (ORCPT ); Mon, 24 Sep 2018 14:45:41 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , "Paul E. McKenney" , Sasha Levin Subject: [PATCH 4.18 204/235] rcutorture: Use monotonic timestamp for stall detection Date: Mon, 24 Sep 2018 13:53:10 +0200 Message-Id: <20180924113124.454528127@linuxfoundation.org> In-Reply-To: <20180924113103.999624566@linuxfoundation.org> References: <20180924113103.999624566@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnd Bergmann [ Upstream commit 622be33fcbc93e9b672b99ed338369eb5e843ac3 ] The get_seconds() call is deprecated because it overflows on 32-bit architectures. The algorithm in rcu_torture_stall() can deal with the overflow, but another problem here is that using a CLOCK_REALTIME stamp can lead to a false-positive stall warning when a settimeofday() happens concurrently. Using ktime_get_seconds() instead avoids those issues and will never overflow. The added cast to 'unsigned long' however is necessary to make ULONG_CMP_LT() work correctly. Signed-off-by: Arnd Bergmann Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/rcu/rcutorture.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1446,7 +1446,7 @@ static int rcu_torture_stall(void *args) VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff"); } if (!kthread_should_stop()) { - stop_at = get_seconds() + stall_cpu; + stop_at = ktime_get_seconds() + stall_cpu; /* RCU CPU stall is expected behavior in following code. */ rcu_read_lock(); if (stall_cpu_irqsoff) @@ -1455,7 +1455,8 @@ static int rcu_torture_stall(void *args) preempt_disable(); pr_alert("rcu_torture_stall start on CPU %d.\n", smp_processor_id()); - while (ULONG_CMP_LT(get_seconds(), stop_at)) + while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(), + stop_at)) continue; /* Induce RCU CPU stall warning. */ if (stall_cpu_irqsoff) local_irq_enable();