From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:41374 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967162AbeCSSJT (ORCPT ); Mon, 19 Mar 2018 14:09:19 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Engraf , John Stultz , Sasha Levin Subject: [PATCH 3.18 16/68] timers, sched_clock: Update timeout for clock wrap Date: Mon, 19 Mar 2018 19:05:54 +0100 Message-Id: <20180319171830.147593353@linuxfoundation.org> In-Reply-To: <20180319171827.899658615@linuxfoundation.org> References: <20180319171827.899658615@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Engraf [ Upstream commit 1b8955bc5ac575009835e371ae55e7f3af2197a9 ] The scheduler clock framework may not use the correct timeout for the clock wrap. This happens when a new clock driver calls sched_clock_register() after the kernel called sched_clock_postinit(). In this case the clock wrap timeout is too long thus sched_clock_poll() is called too late and the clock already wrapped. On my ARM system the scheduler was no longer scheduling any other task than the idle task because the sched_clock() wrapped. Signed-off-by: David Engraf Signed-off-by: John Stultz Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/time/sched_clock.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -146,6 +146,11 @@ void __init sched_clock_register(u64 (*r cd.epoch_ns = ns; raw_write_seqcount_end(&cd.seq); + if (sched_clock_timer.function != NULL) { + /* update timeout for clock wrap */ + hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL); + } + r = rate; if (r >= 4000000) { r /= 1000000;