From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752467AbdKIDC5 (ORCPT ); Wed, 8 Nov 2017 22:02:57 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:42098 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751798AbdKIDCt (ORCPT ); Wed, 8 Nov 2017 22:02:49 -0500 From: Pavel Tatashin To: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, linux@armlinux.org.uk, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, john.stultz@linaro.org, sboyd@codeaurora.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, douly.fnst@cn.fujitsu.com Subject: [PATCH v8 4/6] sched: early boot clock Date: Wed, 8 Nov 2017 22:01:59 -0500 Message-Id: <20171109030201.5991-5-pasha.tatashin@oracle.com> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171109030201.5991-1-pasha.tatashin@oracle.com> References: <20171109030201.5991-1-pasha.tatashin@oracle.com> X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allow sched_clock() to be used before schec_clock_init() and sched_clock_init_late() are called. This provides us with a way to get early boot timestamps on machines with unstable clocks. Signed-off-by: Pavel Tatashin --- kernel/sched/clock.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index e086babe6c61..8bc603951c2d 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -217,6 +217,11 @@ void clear_sched_clock_stable(void) */ static int __init sched_clock_init_late(void) { + /* Transition to unstable clock from early clock */ + local_irq_disable(); + __gtod_offset = sched_clock() + __sched_clock_offset - ktime_get_ns(); + local_irq_enable(); + sched_clock_running = 2; /* * Ensure that it is impossible to not do a static_key update. @@ -362,8 +367,9 @@ u64 sched_clock_cpu(int cpu) if (sched_clock_stable()) return sched_clock() + __sched_clock_offset; - if (unlikely(!sched_clock_running)) - return 0ull; + /* Use early clock until sched_clock_init_late() */ + if (unlikely(sched_clock_running < 2)) + return sched_clock() + __sched_clock_offset; preempt_disable_notrace(); scd = cpu_sdc(cpu); -- 2.15.0