From nobody Sun Feb 8 12:42:54 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37F64EB64D8 for ; Fri, 16 Jun 2023 18:53:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229706AbjFPSxe (ORCPT ); Fri, 16 Jun 2023 14:53:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345156AbjFPSx0 (ORCPT ); Fri, 16 Jun 2023 14:53:26 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D8AE3A9E; Fri, 16 Jun 2023 11:53:22 -0700 (PDT) Date: Fri, 16 Jun 2023 18:53:19 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686941600; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vwwe934FIcaw97RpxpbJdTmS2f0r5fdZZt43SX5cE2I=; b=BojAA2eXo0THrTKJEZbIpojWx9evZe7MU47eHPGhLHbaPCA4AaV/euHLRXdBNIBytdAPDM epV2Ac9WAcLrmg9xXoYQGN8uO4mnr/MXB8C9HIOrQX3uoY4Y7gpn3AbYqOPvyxM3k3MGk1 hKM2HBB1D58LhPQprApVrNrOTsN99rYYi4VQ3wCpgwQkRqj5BZu+I2JIPuy+YiEot603rd jNpoH9+HU1OEttuG8EkrXrJyF7Hvog+3onJGDwonYcK7zOJta9yNdMD8mWxZKRWoOoj5HL 2SjUWR3GxICjTipPDufuqQk5tte59lho7hq6I0Yk34XFgfRT0tLzrg7nxm4v4A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686941600; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vwwe934FIcaw97RpxpbJdTmS2f0r5fdZZt43SX5cE2I=; b=tkIMnXU+b12oBdoyl2GFlPd9wmGyB4UoBkOZvEp7hql83pwsz7qXRQwXu8zxL4obV5XfdV 3v5QnXA07FHsZLBQ== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: timers/urgent] tick/common: Align tick period during sched_timer setup Cc: Mathias Krause , "Bhatnagar, Rishabh" , Thomas Gleixner , Sebastian Andrzej Siewior , "Richard W.M. Jones" , SeongJae Park , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net> References: <5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net> MIME-Version: 1.0 Message-ID: <168694159988.404.1902283865304443546.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the timers/urgent branch of tip: Commit-ID: 13bb06f8dd42071cb9a49f6e21099eea05d4b856 Gitweb: https://git.kernel.org/tip/13bb06f8dd42071cb9a49f6e21099eea0= 5d4b856 Author: Thomas Gleixner AuthorDate: Thu, 15 Jun 2023 11:18:30 +02:00 Committer: Thomas Gleixner CommitterDate: Fri, 16 Jun 2023 20:45:28 +02:00 tick/common: Align tick period during sched_timer setup The tick period is aligned very early while the first clock_event_device is registered. At that point the system runs in periodic mode and switches later to one-shot mode if possible. The next wake-up event is programmed based on the aligned value (tick_next_period) but the delta value, that is used to program the clock_event_device, is computed based on ktime_get(). With the subtracted offset, the device fires earlier than the exact time frame. With a large enough offset the system programs the timer for the next wake-up and the remaining time left is too small to make any boot progress. The system hangs. Move the alignment later to the setup of tick_sched timer. At this point the system switches to oneshot mode and a high resolution clocksource is available. At this point it is safe to align tick_next_period because ktime_get() will now return accurate (not jiffies based) time. [bigeasy: Patch description + testing]. Fixes: e9523a0d81899 ("tick/common: Align tick period with the HZ tick.") Reported-by: Mathias Krause Reported-by: "Bhatnagar, Rishabh" Suggested-by: Mathias Krause Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Tested-by: Richard W.M. Jones Tested-by: Mathias Krause Acked-by: SeongJae Park Cc: stable@vger.kernel.org Link: https://lore.kernel.org/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecuri= ty.net Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.c= om Link: https://lore.kernel.org/r/20230615091830.RxMV2xf_@linutronix.de --- kernel/time/tick-common.c | 13 +------------ kernel/time/tick-sched.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 13 deletions(-) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 65b8658..e9138cd 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -218,19 +218,8 @@ static void tick_setup_device(struct tick_device *td, * this cpu: */ if (tick_do_timer_cpu =3D=3D TICK_DO_TIMER_BOOT) { - ktime_t next_p; - u32 rem; - tick_do_timer_cpu =3D cpu; - - next_p =3D ktime_get(); - div_u64_rem(next_p, TICK_NSEC, &rem); - if (rem) { - next_p -=3D rem; - next_p +=3D TICK_NSEC; - } - - tick_next_period =3D next_p; + tick_next_period =3D ktime_get(); #ifdef CONFIG_NO_HZ_FULL /* * The boot CPU may be nohz_full, in which case set diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 5225467..42c0be3 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -161,8 +161,19 @@ static ktime_t tick_init_jiffy_update(void) raw_spin_lock(&jiffies_lock); write_seqcount_begin(&jiffies_seq); /* Did we start the jiffies update yet ? */ - if (last_jiffies_update =3D=3D 0) + if (last_jiffies_update =3D=3D 0) { + u32 rem; + + /* + * Ensure that the tick is aligned to a multiple of + * TICK_NSEC. + */ + div_u64_rem(tick_next_period, TICK_NSEC, &rem); + if (rem) + tick_next_period +=3D TICK_NSEC - rem; + last_jiffies_update =3D tick_next_period; + } period =3D last_jiffies_update; write_seqcount_end(&jiffies_seq); raw_spin_unlock(&jiffies_lock);