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 80446C636CC for ; Sat, 11 Feb 2023 10:31:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229960AbjBKKbA (ORCPT ); Sat, 11 Feb 2023 05:31:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229666AbjBKKa4 (ORCPT ); Sat, 11 Feb 2023 05:30:56 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77A022196B; Sat, 11 Feb 2023 02:30:55 -0800 (PST) Date: Sat, 11 Feb 2023 10:30:53 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1676111454; 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=ungYDX7qzyRMeHGhhRpZSXmVK1Nj64kF59rGW+NJBKg=; b=46hDFntxGBqknSmVIMYVDAoo8H2Ohd7rmP7Sv3aoeTgTINHnlpYWldTpklVW3Kj27fgehK ncJqUc/0HItXG0muxrd5rHqy6zSeXWG4e17JXq6OUVmrHV8UKVaJ29oivq23hN/hMfdy7t 0mtNZhWLfso/3kUtmFgUeHIr/9/A/GOXHbAuKO+Z8XDHnmS6idRozbvHscfckQI3a2wHMK B1mF+ryvvHZ8KTy9eTh/VRbcTl/wUluxJE7fiRxKSawTAT+zRnlxl5sX3z75/C7RrHt3Se +yU3eaALFahvg4dJcPHTeULyLKRedcTmZ0HknBnGD8Vb2UiM+VwtR/U0rQxKtQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1676111454; 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=ungYDX7qzyRMeHGhhRpZSXmVK1Nj64kF59rGW+NJBKg=; b=NepQjkASgEDH9BLtmMskoC1VpKVt5P0CA1udotDSVRT9mV5uLgyuWR5hvZVUOaNvrwi5w9 vEwNXFgjrRDpR+DA== From: "tip-bot2 for Valentin Schneider" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/deadline: Add more reschedule cases to prio_changed_dl() Cc: Valentin Schneider , "Peter Zijlstra (Intel)" , Juri Lelli , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230206140612.701871-1-vschneid@redhat.com> References: <20230206140612.701871-1-vschneid@redhat.com> MIME-Version: 1.0 Message-ID: <167611145381.4906.16019956049524655182.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: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 7ea98dfa44917a201e76d4fe96bf61d76e60f524 Gitweb: https://git.kernel.org/tip/7ea98dfa44917a201e76d4fe96bf61d76e60f524 Author: Valentin Schneider AuthorDate: Mon, 06 Feb 2023 14:06:12 Committer: Peter Zijlstra CommitterDate: Sat, 11 Feb 2023 11:18:10 +01:00 sched/deadline: Add more reschedule cases to prio_changed_dl() I've been tracking down an issue on a ~5.17ish kernel where: CPUx CPUy

[idle task keeps running here until *something* accidentally sets TIF_NEED_RESCHED] On that kernel, it is quite easy to trigger using rt-tests's deadline_test [1] with the test running on isolated CPUs (this reduces the chance of something unrelated setting TIF_NEED_RESCHED on the idle tasks, making the issue even more obvious as the hung task detector chimes in). I haven't been able to reproduce this using a mainline kernel, even if I revert 2972e3050e35 ("tracing: Make trace_marker{,_raw} stream-like") which gets rid of the lock involved in the above test, *but* I cannot convince myself the issue isn't there from looking at the code. Make prio_changed_dl() issue a reschedule if the current task isn't a deadline one. While at it, ensure a reschedule is emitted when a queued-but-not-current task gets boosted with an earlier deadline that current's. [1]: https://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juri Lelli Link: https://lore.kernel.org/r/20230206140612.701871-1-vschneid@redhat.com --- kernel/sched/deadline.c | 42 +++++++++++++++++++++++++--------------- 1 file changed, 27 insertions(+), 15 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 0d97d54..71b2437 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2663,17 +2663,20 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) static void prio_changed_dl(struct rq *rq, struct task_struct *p, int oldprio) { - if (task_on_rq_queued(p) || task_current(rq, p)) { + if (!task_on_rq_queued(p)) + return; + #ifdef CONFIG_SMP - /* - * This might be too much, but unfortunately - * we don't have the old deadline value, and - * we can't argue if the task is increasing - * or lowering its prio, so... - */ - if (!rq->dl.overloaded) - deadline_queue_pull_task(rq); + /* + * This might be too much, but unfortunately + * we don't have the old deadline value, and + * we can't argue if the task is increasing + * or lowering its prio, so... + */ + if (!rq->dl.overloaded) + deadline_queue_pull_task(rq); + if (task_current(rq, p)) { /* * If we now have a earlier deadline task than p, * then reschedule, provided p is still on this @@ -2681,15 +2684,24 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p, */ if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline)) resched_curr(rq); -#else + } else { /* - * Again, we don't know if p has a earlier - * or later deadline, so let's blindly set a - * (maybe not needed) rescheduling point. + * Current may not be deadline in case p was throttled but we + * have just replenished it (e.g. rt_mutex_setprio()). + * + * Otherwise, if p was given an earlier deadline, reschedule. */ - resched_curr(rq); -#endif /* CONFIG_SMP */ + if (!dl_task(rq->curr) || + dl_time_before(p->dl.deadline, rq->curr->dl.deadline)) + resched_curr(rq); } +#else + /* + * We don't know if p has a earlier or later deadline, so let's blindly + * set a (maybe not needed) rescheduling point. + */ + resched_curr(rq); +#endif } DEFINE_SCHED_CLASS(dl) = {