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 59EFBCD80D5 for ; Tue, 10 Oct 2023 13:54:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231987AbjJJNy3 (ORCPT ); Tue, 10 Oct 2023 09:54:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232465AbjJJNy3 (ORCPT ); Tue, 10 Oct 2023 09:54:29 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F9F39D; Tue, 10 Oct 2023 06:54:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=/Q2326nbgNVkzW/VEHSwQCD8IL326flLiX2/oxCqN0g=; b=vwbk4OYTkj+i5hVlzwFJfLP7V8 4Wca/Me2pvYsVPi5UmFxhBkFS2Rli0Hl4cs3XiY/gVPYh2aix9MnSTDlNIJ1ZNSSubRiUeGiKI4Fd 2uCUvvOpNsOvFMl5ogtHz4C5x1aZ6HSBk5DICSeyAwynTDnoBUftyKtkB6W5p0mFppUxUnSzIN/1N +pgD6/DpPlv1Y08Yrn8y+1qnByWbjf0VmLnW6qiy82RHDXOmZg9dgpk7g6xYtBRVi87Hlz0lzSSye 8BZOoxEinlmAC2yhdWhncDkg+yQ+sAAalCckfYRhlMdHLmcSgsGAdJ0NETgV1px/iZcwY7oOnzzUQ wnfhJOkw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qqDB6-004xnI-KK; Tue, 10 Oct 2023 13:53:40 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 4E225300392; Tue, 10 Oct 2023 15:53:40 +0200 (CEST) Date: Tue, 10 Oct 2023 15:53:40 +0200 From: Peter Zijlstra To: Hao Jia Cc: mingo@redhat.com, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Igor Raits , Bagas Sanjaya Subject: Re: [External] Re: [PATCH] sched/core: Fix wrong warning check in rq_clock_start_loop_update() Message-ID: <20231010135340.GK377@noisy.programming.kicks-ass.net> References: <20230913082424.73252-1-jiahao.os@bytedance.com> <20230928114159.GJ9829@noisy.programming.kicks-ass.net> <979f948c-7611-b137-a06a-ca09ff63f919@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <979f948c-7611-b137-a06a-ca09ff63f919@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Oct 07, 2023 at 04:44:46PM +0800, Hao Jia wrote: > > That is, would not something like the below make more sense? > > If we understand correctly, this may not work. > > After applying this patch, the following situation will trigger the > rq->clock_update_flags < RQCF_ACT_SKIP warning. > > If rq_clock_skip_update() is called before __schedule(), so RQCF_REQ_SKIP of > rq->clock_update_flags is set. > > > > > __schedule() { > rq_lock(rq, &rf); [rq->clock_update_flags is RQCF_REQ_SKIP] > rq->clock_update_flags <<= 1; > update_rq_clock(rq); [rq->clock_update_flags is RQCF_ACT_SKIP] > + rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); > * At this time, rq->clock_update_flags = 0; * Fixed easily enough, just change to: rq->clock_updated_flags = RQCF_UPDATED; > > pick_next_task_fair > set_next_entity > update_load_avg > assert_clock_updated() <--- > } --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a0a582c8cf8c..cf9eb1a26c22 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5357,8 +5357,6 @@ context_switch(struct rq *rq, struct task_struct *prev, /* switch_mm_cid() requires the memory barriers above. */ switch_mm_cid(rq, prev, next); - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - prepare_lock_switch(rq, next, rf); /* Here we just switch the register state and the stack. */ @@ -6596,6 +6594,7 @@ static void __sched notrace __schedule(unsigned int sched_mode) /* Promote REQ to ACT */ rq->clock_update_flags <<= 1; update_rq_clock(rq); + rq->clock_update_flags = RQCF_UPDATED; switch_count = &prev->nivcsw; @@ -6675,8 +6674,6 @@ static void __sched notrace __schedule(unsigned int sched_mode) /* Also unlocks the rq: */ rq = context_switch(rq, prev, next, &rf); } else { - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq);