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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 14A45C43387 for ; Mon, 7 Jan 2019 12:52:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9FFB20651 for ; Mon, 7 Jan 2019 12:52:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="lo47j8WI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729605AbfAGMwp (ORCPT ); Mon, 7 Jan 2019 07:52:45 -0500 Received: from merlin.infradead.org ([205.233.59.134]:36740 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727446AbfAGMwn (ORCPT ); Mon, 7 Jan 2019 07:52:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zXL2g+LrqH5SxJjQrxx6sdVW+HEYZs9gYkrT3nrA67Q=; b=lo47j8WIWi90J+BuKXe4Zek9u QuTuFYL6/y8wMXmDsMkzIZjfsRIDtoa7KgcMiargg073BgJCOVAU6ICijKfdOtJYz3yTBd/Qcl60Q fsr5L4ZewovxuTzOp0Qz79MUa0A1VU7sEIPYlxalW21EFLRfcX03xysNrgWX8sz0L+t4ojAgZcoXn kLopHg/lFe3byKnMDBS8RQvFPKjHKIMSfmUprpz4NmrpqKIiekD2WS0iqRu6QkD2BHHKqKleXt7Yj 4VRXnMNCRPQ3/35KP7nqYYpB9cJrJB2hRN0whN/tMrN1h83Hin+hg+qD15jef1a4ZWlEXns49YzsS kq+TPjzvw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ggUOQ-0004We-Kf; Mon, 07 Jan 2019 12:52:35 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3529E20074A04; Mon, 7 Jan 2019 13:52:31 +0100 (CET) Date: Mon, 7 Jan 2019 13:52:31 +0100 From: Peter Zijlstra To: Mike Galbraith Cc: Tom Putzeys , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , Sebastian Andrzej Siewior , Thomas Gleixner Subject: Re: CFS scheduler: spin_lock usage causes dead lock when smp_apic_timer_interrupt occurs Message-ID: <20190107125231.GE14122@hirez.programming.kicks-ass.net> References: <20190107102613.GC2861@worktop.programming.kicks-ass.net> <1546864114.26963.5.camel@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1546864114.26963.5.camel@gmx.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 07, 2019 at 01:28:34PM +0100, Mike Galbraith wrote: > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 960ad0ce77d7..420624c49f38 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5007,9 +5007,9 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) > cfs_b->period = ns_to_ktime(default_cfs_period()); > > INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); > - hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); > + hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD); > cfs_b->period_timer.function = sched_cfs_period_timer; > - hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > + hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); > cfs_b->slack_timer.function = sched_cfs_slack_timer; > } Right, that should sort it. But I'm not sure this is the best solution though. That cfs-runtime crud can (IIRC) iterate lists etc.. so running it from the softirq isn't a bad idea. We just need to fix that locking up a bit. Something a wee bit like so perhaps.. --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 13776fac7b74..3cfe26aa098a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4566,7 +4566,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, struct rq *rq = rq_of(cfs_rq); struct rq_flags rf; - rq_lock(rq, &rf); + rq_lock_irqsave(rq, &rf); if (!cfs_rq_throttled(cfs_rq)) goto next; @@ -4583,7 +4583,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, unthrottle_cfs_rq(cfs_rq); next: - rq_unlock(rq, &rf); + rq_unlock_irqrestore(rq, &rf); if (!remaining) break; @@ -4599,7 +4599,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, * period the timer is deactivated until scheduling resumes; cfs_b->idle is * used to track this state. */ -static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) +static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags) { u64 runtime, runtime_expires; int throttled; @@ -4641,11 +4641,11 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) { runtime = cfs_b->runtime; cfs_b->distribute_running = 1; - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); /* we can't nest cfs_b->lock while distributing bandwidth */ runtime = distribute_cfs_runtime(cfs_b, runtime, runtime_expires); - raw_spin_lock(&cfs_b->lock); + raw_spin_lock_irqsave(&cfs_b->lock, flags); cfs_b->distribute_running = 0; throttled = !list_empty(&cfs_b->throttled_cfs_rq); @@ -4754,17 +4754,18 @@ static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) { u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); + unsigned long flags; u64 expires; /* confirm we're still not at a refresh boundary */ - raw_spin_lock(&cfs_b->lock); + raw_spin_lock_irqsave(&cfs_b->lock, flags); if (cfs_b->distribute_running) { - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); return; } if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); return; } @@ -4775,18 +4776,18 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) if (runtime) cfs_b->distribute_running = 1; - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); if (!runtime) return; runtime = distribute_cfs_runtime(cfs_b, runtime, expires); - raw_spin_lock(&cfs_b->lock); + raw_spin_lock_irqsave(&cfs_b->lock, flags); if (expires == cfs_b->runtime_expires) lsub_positive(&cfs_b->runtime, runtime); cfs_b->distribute_running = 0; - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); } /* @@ -4864,20 +4865,21 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) { struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, period_timer); + unsigned long flags; int overrun; int idle = 0; - raw_spin_lock(&cfs_b->lock); + raw_spin_lock_irqsave(&cfs_b->lock, flags); for (;;) { overrun = hrtimer_forward_now(timer, cfs_b->period); if (!overrun) break; - idle = do_sched_cfs_period_timer(cfs_b, overrun); + idle = do_sched_cfs_period_timer(cfs_b, overrun, flags); } if (idle) cfs_b->period_active = 0; - raw_spin_unlock(&cfs_b->lock); + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; }