From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933004AbaHHUxW (ORCPT ); Fri, 8 Aug 2014 16:53:22 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:41251 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932954AbaHHUxP (ORCPT ); Fri, 8 Aug 2014 16:53:15 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Rafael J. Wysocki" , Viresh Kumar , Bin Gao , Linus Torvalds , Mika Westerberg , Paul Gortmaker , Stefani Seibold , Peter Zijlstra , Ingo Molnar , Kamal Mostafa Subject: [PATCH 3.13 110/259] x86, tsc: Fix cpufreq lockup Date: Fri, 8 Aug 2014 13:38:53 -0700 Message-Id: <1407530482-4483-111-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1407530482-4483-1-git-send-email-kamal@canonical.com> References: <1407530482-4483-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 3896c329df8092661dac80f55a8c3f60136fd61a upstream. Mauro reported that his AMD X2 using the powernow-k8 cpufreq driver locked up when doing cpu hotplug. Because we called set_cyc2ns_scale() from the time_cpufreq_notifier() unconditionally, it gets called multiple times for each freq change, instead of only the once, when the tsc_khz value actually changes. Because it gets called more than once, we run out of cyc2ns data slots and stall, waiting for a free one, but because we're half way offline, there's no consumers to free slots. By placing the call inside the condition that actually changes tsc_khz we avoid superfluous calls and avoid the problem. Reported-by: Mauro Tested-by: Mauro Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs") Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Cc: Bin Gao Cc: Linus Torvalds Cc: Mika Westerberg Cc: Paul Gortmaker Cc: Stefani Seibold Cc: linux-kernel@vger.kernel.org Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar Signed-off-by: Kamal Mostafa --- arch/x86/kernel/tsc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 930e5d4..66af9af 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -722,9 +722,9 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); if (!(freq->flags & CPUFREQ_CONST_LOOPS)) mark_tsc_unstable("cpufreq changes"); - } - set_cyc2ns_scale(tsc_khz, freq->cpu); + set_cyc2ns_scale(tsc_khz, freq->cpu); + } return 0; } -- 1.9.1