From nobody Mon Dec 29 04:56:59 2025 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 35A38C4167B for ; Fri, 1 Dec 2023 09:27:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378120AbjLAJ1n (ORCPT ); Fri, 1 Dec 2023 04:27:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378055AbjLAJ1W (ORCPT ); Fri, 1 Dec 2023 04:27:22 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3A521725 for ; Fri, 1 Dec 2023 01:27:15 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nZi/SXfoi2GICSzM+IYBAVSlO8Hm1DXEFr76jQHYOZ0=; b=lPUu/u3782O76F4tssDfbbwJSu1UYJWRXA1YF1HFvK1m8kbs0zLQsUh/Qrq0SympHt1Xn4 fWs6pLLsziRXsDGGtVSkmgIluUmEPyOt49N0oJuW1GpqQsDrQiTwLCGHDYPxL2sHNl8pO8 uZrfXgDRa3Soql/IDz++WAZHigpe67VrkWm7MrhlkMdDJb1cuTVJRBpNVrj0k0qs67dVi3 SnfBc962XKiwdxw27XZSz4hJUgXOfPYnpxuSOBDbSvDj36Sfa0N/0H08AMFC8K3OePFC/t LsAllTQBY9b+fu99vTafsfRYXEb2PxTXLZsynXnrqJJ34TflfOYmg29flJ7ItA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nZi/SXfoi2GICSzM+IYBAVSlO8Hm1DXEFr76jQHYOZ0=; b=DGxDnst2vjquka22zFxBnL29sukEirkFvC4s2bWFecYQdCP9TQh2tKsQYBTAwCLj3xIhX6 heDteX2CRHR+6lAg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 12/32] timers: Fix nextevt calculation when no timers are pending Date: Fri, 1 Dec 2023 10:26:34 +0100 Message-Id: <20231201092654.34614-13-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When no timer is queued into an empty timer base, the next_expiry will not be updated. It was originally calculated as base->clk + NEXT_TIMER_MAX_DELTA When the timer base stays empty long enough (> NEXT_TIMER_MAX_DELTA), the next_expiry value of the empty base suggests that there is a timer pending soon. This might be more a kind of a theoretical problem, but the fix doesn't hurt. Use only base->next_expiry value as nextevt when timers are pending. Otherwise nextevt will be jiffies + NEXT_TIMER_MAX_DELTA. As all information is in place, update base->next_expiry value of the empty timer base as well. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: New patch --- kernel/time/timer.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 0826018d9873..4dffe966424c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1922,8 +1922,8 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expi= res) u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + unsigned long nextevt =3D basej + NEXT_TIMER_MAX_DELTA; u64 expires =3D KTIME_MAX; - unsigned long nextevt; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -1935,7 +1935,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64= basem) raw_spin_lock(&base->lock); if (base->next_expiry_recalc) next_expiry_recalc(base); - nextevt =3D base->next_expiry; =20 /* * We have a fresh next event. Check whether we can forward the @@ -1944,10 +1943,20 @@ u64 get_next_timer_interrupt(unsigned long basej, u= 64 basem) __forward_timer_base(base, basej); =20 if (base->timers_pending) { + nextevt =3D base->next_expiry; + /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; + } else { + /* + * Move next_expiry for the empty base into the future to + * prevent a unnecessary raise of the timer softirq when the + * next_expiry value will be reached even if there is no timer + * pending. + */ + base->next_expiry =3D nextevt; } =20 /* --=20 2.39.2