From mboxrd@z Thu Jan 1 00:00:00 1970 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 1C383EB64DC for ; Mon, 26 Jun 2023 18:44:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232571AbjFZSoJ (ORCPT ); Mon, 26 Jun 2023 14:44:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232568AbjFZSoH (ORCPT ); Mon, 26 Jun 2023 14:44:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3988AC for ; Mon, 26 Jun 2023 11:44:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6366860F30 for ; Mon, 26 Jun 2023 18:44:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69F29C433C8; Mon, 26 Jun 2023 18:44:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687805045; bh=xNQ54ytPvumoCeiLgJc7OnP+1PsgOlLIuIcEDfadQF8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O6b8ukvnENt0ooKhdmkZ462pe0PXsF55zr2S4R8p9SN/1TRCNfCfU2PO0ZjPmZvOM ACa7VA8HOKO3FmUQqiEoWdktlpTXwkFrGV8ADfLstrS3JWRaPGuhwkPsrjzX2qUE5I WyCJNDgf0MtfqMQOi3yMhQMCcP8/HRLmja4zt7JQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mathias Krause , "Bhatnagar, Rishabh" , Thomas Gleixner , Sebastian Andrzej Siewior , "Richard W.M. Jones" , SeongJae Park Subject: [PATCH 5.10 04/81] tick/common: Align tick period during sched_timer setup Date: Mon, 26 Jun 2023 20:11:46 +0200 Message-ID: <20230626180744.637066310@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230626180744.453069285@linuxfoundation.org> References: <20230626180744.453069285@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Thomas Gleixner commit 13bb06f8dd42071cb9a49f6e21099eea05d4b856 upstream. 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@grsecurity.net Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com Link: https://lore.kernel.org/r/20230615091830.RxMV2xf_@linutronix.de Signed-off-by: Greg Kroah-Hartman --- kernel/time/tick-common.c | 13 +------------ kernel/time/tick-sched.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 13 deletions(-) --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -216,19 +216,8 @@ static void tick_setup_device(struct tic * this cpu: */ if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { - ktime_t next_p; - u32 rem; - tick_do_timer_cpu = cpu; - - next_p = ktime_get(); - div_u64_rem(next_p, TICK_NSEC, &rem); - if (rem) { - next_p -= rem; - next_p += TICK_NSEC; - } - - tick_next_period = next_p; + tick_next_period = ktime_get(); #ifdef CONFIG_NO_HZ_FULL /* * The boot CPU may be nohz_full, in which case set --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -129,8 +129,19 @@ static ktime_t tick_init_jiffy_update(vo raw_spin_lock(&jiffies_lock); write_seqcount_begin(&jiffies_seq); /* Did we start the jiffies update yet ? */ - if (last_jiffies_update == 0) + if (last_jiffies_update == 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 += TICK_NSEC - rem; + last_jiffies_update = tick_next_period; + } period = last_jiffies_update; write_seqcount_end(&jiffies_seq); raw_spin_unlock(&jiffies_lock);