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 C01F2C433F5 for ; Wed, 20 Apr 2022 19:12:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354704AbiDTTPA (ORCPT ); Wed, 20 Apr 2022 15:15:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347774AbiDTTO4 (ORCPT ); Wed, 20 Apr 2022 15:14:56 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B94D845054 for ; Wed, 20 Apr 2022 12:12:09 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 56BF81477; Wed, 20 Apr 2022 12:12:09 -0700 (PDT) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D29213F766; Wed, 20 Apr 2022 12:12:07 -0700 (PDT) Message-ID: Date: Wed, 20 Apr 2022 21:11:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 From: Dietmar Eggemann Subject: Re: [External] Re: [PATCH] sched/core: Avoid obvious double update_rq_clock warning To: Hao Jia , Peter Zijlstra Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org References: <20220418090929.54005-1-jiahao.os@bytedance.com> <20220419104828.GQ2731@worktop.programming.kicks-ass.net> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/04/2022 10:29, Hao Jia wrote: > On 4/19/22 6:48 PM, Peter Zijlstra wrote: >> On Mon, Apr 18, 2022 at 05:09:29PM +0800, Hao Jia wrote: [...] >> I'm really not sure about this part though. This is a bit of a mess. The >> balancer doesn't really need the pinning stuff. I realize you did that >> because we got the clock annotation mixed up with that, but urgh. >> >> Basically we want double_rq_lock() / double_lock_balance() to clear >> RQCF_UPDATED, right? Perhaps do that directly? >> >> (maybe with an inline helper and a wee comment?) >> >> The only immediate problem with this would appear to be that >> _double_rq_lock() behaves differently when it returns 0. Not sure that >> matters. >> >> Hmm? > > Thanks for your review comments. > As you have prompted, the WARN_DOUBLE_CLOCK warning is still triggered > when _double_rq_lock() returns 0. > Please review the solution below, and based on your review, I will > submit the v2 patch as soon as possible. > Thanks. [...] Maybe something like this: -->8-- From: Dietmar Eggemann Date: Wed, 20 Apr 2022 11:12:10 +0200 Subject: [PATCH] sched/core: Clear RQCF_UPDATED in _double_lock_balance() & double_rq_lock() Signed-off-by: Dietmar Eggemann --- kernel/sched/core.c | 6 +++--- kernel/sched/sched.h | 20 ++++++++++++++++---- 2 files changed, 19 insertions(+), 7 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 068c088e9584..f4cfe7eea861 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -610,10 +610,10 @@ void double_rq_lock(struct rq *rq1, struct rq *rq2) swap(rq1, rq2); raw_spin_rq_lock(rq1); - if (__rq_lockp(rq1) == __rq_lockp(rq2)) - return; + if (__rq_lockp(rq1) != __rq_lockp(rq2)) + raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); - raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); + rq_clock_clear_update(rq1, rq2); } #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 58263f90c559..3a77b10d7cc4 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2515,6 +2515,16 @@ static inline bool rq_order_less(struct rq *rq1, struct rq *rq2) extern void double_rq_lock(struct rq *rq1, struct rq *rq2); +#ifdef CONFIG_SCHED_DEBUG +static inline void rq_clock_clear_update(struct rq *rq1, struct rq *rq2) +{ + rq1->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); + rq2->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); +} +#else +static inline void rq_clock_clear_update(struct rq *rq1, struct rq *rq2) {} +#endif + #ifdef CONFIG_PREEMPTION /* @@ -2549,14 +2559,15 @@ static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest) __acquires(busiest->lock) __acquires(this_rq->lock) { - if (__rq_lockp(this_rq) == __rq_lockp(busiest)) - return 0; - - if (likely(raw_spin_rq_trylock(busiest))) + if (__rq_lockp(this_rq) == __rq_lockp(busiest) || + likely(raw_spin_rq_trylock(busiest))) { + rq_clock_clear_update(this_rq, busiest); return 0; + } if (rq_order_less(this_rq, busiest)) { raw_spin_rq_lock_nested(busiest, SINGLE_DEPTH_NESTING); + rq_clock_clear_update(this_rq, busiest); return 0; } @@ -2650,6 +2661,7 @@ static inline void double_rq_lock(struct rq *rq1, struct rq *rq2) BUG_ON(rq1 != rq2); raw_spin_rq_lock(rq1); __acquire(rq2->lock); /* Fake it out ;) */ + rq_clock_clear_update(rq1, rq2); } /* -- 2.25.1