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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79919C282E1 for ; Tue, 23 Apr 2019 20:51:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 483E6217D9 for ; Tue, 23 Apr 2019 20:51:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556052687; bh=RUmyJMiqx5WMqptfB+MnJRlO0ZxnMDfONnarSyNAONA=; h=Subject:To:Cc:From:Date:List-ID:From; b=sQXQxok0sEVKwTmDwYKfQ1HAIEv+FGE7F9badrjYx9lNXZmUbcHkBsGcJIrnAW3Zv fCf3P7/MO4Xxpk0HLlwfkZlH6zolTWvbWljoe9UCR1vljRW9Nop/ReCGklxSWs5G29 20JWatWN2T03E2+K2qicF/KE4XyqKIl22upPObE0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727378AbfDWUv0 (ORCPT ); Tue, 23 Apr 2019 16:51:26 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:41041 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726157AbfDWUv0 (ORCPT ); Tue, 23 Apr 2019 16:51:26 -0400 Received: from compute6.internal (compute6.nyi.internal [10.202.2.46]) by mailout.nyi.internal (Postfix) with ESMTP id B42342204E; Tue, 23 Apr 2019 16:51:25 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute6.internal (MEProxy); Tue, 23 Apr 2019 16:51:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=Cc+zqk 89X5/3M7TJtaiLPsdFjpGfhjcLCk7gA+EZeKo=; b=EldLhw+Dij0QhhmeQjY4M5 B9hCmPFR4D9G7qu3OCrh6ZyP1XYExoi7Io7JroN3OrlarasPBgPU1BgijRFjjxK6 MwQ6E56eLvbKPKsUeyMfwQyUhgQkMmks8WfUex/484RXdLnwmpKkcCvyVKNajyd5 QQJPo308/3yC5u6zbunGZJcmrg1cumcGUPt4pReNATeIRLzv6NNGrmyc2QW0UFWZ RTMNYFkQwETIYR3C8N38FN/uYpP7ThRay+MIexatpdbaYJQczpq55WbGxrTk5+14 eC0M55lr07qm7flWsWUkoFIQfG0fA1uL40f++/y6fR0CJL3Ftvg0g3qpDUuh7oZw == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduuddrgeekgddugedvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucenucfjughrpefuvffhfffkgggtgfesthekredttd dtlfenucfhrhhomhepoehgrhgvghhkhheslhhinhhugihfohhunhgurghtihhonhdrohhr gheqnecuffhomhgrihhnpehkvghrnhgvlhdrohhrghenucfkphepiedvrdduleefrdehtd drvddvleenucfrrghrrghmpehmrghilhhfrhhomhepghhrvghgsehkrhhorghhrdgtohhm necuvehluhhsthgvrhfuihiivgepfe X-ME-Proxy: Received: from localhost (62-193-50-229.as16211.net [62.193.50.229]) by mail.messagingengine.com (Postfix) with ESMTPA id 2670D103C9; Tue, 23 Apr 2019 16:51:25 -0400 (EDT) Subject: FAILED: patch "[PATCH] sched/fair: Limit sched_cfs_period_timer() loop to avoid hard" failed to apply to 4.4-stable tree To: pauld@redhat.com, anton@ozlabs.org, bsegall@google.com, mingo@kernel.org, peterz@infradead.org, stable@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: From: Date: Tue, 23 Apr 2019 22:51:19 +0200 Message-ID: <155605267974249@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 2e8e19226398db8265a8e675fcc0118b9e80c9e8 Mon Sep 17 00:00:00 2001 From: Phil Auld Date: Tue, 19 Mar 2019 09:00:05 -0400 Subject: [PATCH] sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup With extremely short cfs_period_us setting on a parent task group with a large number of children the for loop in sched_cfs_period_timer() can run until the watchdog fires. There is no guarantee that the call to hrtimer_forward_now() will ever return 0. The large number of children can make do_sched_cfs_period_timer() take longer than the period. NMI watchdog: Watchdog detected hard LOCKUP on cpu 24 RIP: 0010:tg_nop+0x0/0x10 walk_tg_tree_from+0x29/0xb0 unthrottle_cfs_rq+0xe0/0x1a0 distribute_cfs_runtime+0xd3/0xf0 sched_cfs_period_timer+0xcb/0x160 ? sched_cfs_slack_timer+0xd0/0xd0 __hrtimer_run_queues+0xfb/0x270 hrtimer_interrupt+0x122/0x270 smp_apic_timer_interrupt+0x6a/0x140 apic_timer_interrupt+0xf/0x20 To prevent this we add protection to the loop that detects when the loop has run too many times and scales the period and quota up, proportionally, so that the timer can complete before then next period expires. This preserves the relative runtime quota while preventing the hard lockup. A warning is issued reporting this state and the new values. Signed-off-by: Phil Auld Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Anton Blanchard Cc: Ben Segall Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190319130005.25492-1-pauld@redhat.com Signed-off-by: Ingo Molnar diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 40bd1e27b1b7..a4d9e14bf138 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4885,6 +4885,8 @@ static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) return HRTIMER_NORESTART; } +extern const u64 max_cfs_quota_period; + static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) { struct cfs_bandwidth *cfs_b = @@ -4892,6 +4894,7 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) unsigned long flags; int overrun; int idle = 0; + int count = 0; raw_spin_lock_irqsave(&cfs_b->lock, flags); for (;;) { @@ -4899,6 +4902,28 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) if (!overrun) break; + if (++count > 3) { + u64 new, old = ktime_to_ns(cfs_b->period); + + new = (old * 147) / 128; /* ~115% */ + new = min(new, max_cfs_quota_period); + + cfs_b->period = ns_to_ktime(new); + + /* since max is 1s, this is limited to 1e9^2, which fits in u64 */ + cfs_b->quota *= new; + cfs_b->quota = div64_u64(cfs_b->quota, old); + + pr_warn_ratelimited( + "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us %lld, cfs_quota_us = %lld)\n", + smp_processor_id(), + div_u64(new, NSEC_PER_USEC), + div_u64(cfs_b->quota, NSEC_PER_USEC)); + + /* reset count so we don't come right back in here */ + count = 0; + } + idle = do_sched_cfs_period_timer(cfs_b, overrun, flags); } if (idle)