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 B9E29C433F5 for ; Tue, 8 Mar 2022 17:41:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349223AbiCHRmK (ORCPT ); Tue, 8 Mar 2022 12:42:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346585AbiCHRmK (ORCPT ); Tue, 8 Mar 2022 12:42:10 -0500 Received: from mail-pg1-x533.google.com (mail-pg1-x533.google.com [IPv6:2607:f8b0:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6384653B66 for ; Tue, 8 Mar 2022 09:41:13 -0800 (PST) Received: by mail-pg1-x533.google.com with SMTP id o23so17056719pgk.13 for ; Tue, 08 Mar 2022 09:41:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=fdTk4aYquZTIk9aPhP7DqM2Gxsxd3HuYNcTcih9MUlU=; b=iMAOKf3zl4qCHt1XZ0nGKGE65C8mjYz3b1xzdmyGig1ijiRkXw+4jB2MGTAUm4tfnd UebN0kQ9pXWaqUsDbrYmAaPJWO1+HvZJkI8QOuxs/8ND/tN1/23iPiiTr0yPnryDF0ZE IyaVTR3zBl1juxUvIaoC3IwfcyvgsYVm/8mJSlvDkPPg6cN4MBc4et4NxXb1yGSlvzCj hw9WcGUTWkvDQSUqLvOXTrp/ukeJklvFREOvYGC2d9yUOONeIjk+JM0v9zx17FR1dq33 oH4KG4rQHNlC7O3RsTowLVcorX42fFu6vfaCQRIEYnd8CndREhcUyNfXJ9OTXajpKST6 GjcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=fdTk4aYquZTIk9aPhP7DqM2Gxsxd3HuYNcTcih9MUlU=; b=WnrhM+wGefsgL0HVhEJqv7s4G6dMXj2mdCZxz+Ja7fyYDCA04+3MiI4mCE8BAITS6z A+VzGMWa3zGIX1Fyyra0NJmUbOPLPZZxbIpdNLFKw7fLhVrMB5RhJcFB08EFe+lBG91z pRwCQ18++P+lT5dpdkBD/BdAoU1PSBdc91lhRuAoH8KwJGgRrsilDBGeIl63BwMnJVqj TE0Ogaolwd0pRO9RHgFAdjWjZSQMbCb5vx0pm02hA0Vf73K7/5MFA1U5ubNTBvVI3umh Ac23UiYoYoTObmicl0huXPZQyIp3athkXZVDhchgxN8pX7cgc6BbXcAQSMlzW/ac8swZ WQ/Q== X-Gm-Message-State: AOAM532x68joQ7K8ri0Pkh8ODJIPQhSGaj4W0nsZayQraTqYKI/Pgkl5 VCr0SbWdzFDUyZlKkZt5NM94mSZSVJU= X-Google-Smtp-Source: ABdhPJxXnwJGrLzNZwn6eQDyYjwzGGbh7RRKQ6ybShnYyN9Ay7t+rlTEHlZLzMTpuo+6FqqBqVQvPA== X-Received: by 2002:a63:ef4f:0:b0:375:6898:f6b8 with SMTP id c15-20020a63ef4f000000b003756898f6b8mr15186903pgk.59.1646761272552; Tue, 08 Mar 2022 09:41:12 -0800 (PST) Received: from google.com ([2620:15c:211:201:ec3e:a6ab:7b5b:ed81]) by smtp.gmail.com with ESMTPSA id b2-20020a056a000a8200b004f1111c66afsm22161988pfl.148.2022.03.08.09.41.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Mar 2022 09:41:12 -0800 (PST) Sender: Minchan Kim Date: Tue, 8 Mar 2022 09:41:09 -0800 From: Minchan Kim To: Marcelo Tosatti Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , Mel Gorman , Nicolas Saenz Julienne , Juri Lelli , Thomas Gleixner , Sebastian Andrzej Siewior , "Paul E. McKenney" , Andrew Morton Subject: Re: [patch v4] mm: lru_cache_disable: replace work queue synchronization with synchronize_rcu Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 04, 2022 at 01:29:31PM -0300, Marcelo Tosatti wrote: > > On systems that run FIFO:1 applications that busy loop > on isolated CPUs, executing tasks on such CPUs under > lower priority is undesired (since that will either > hang the system, or cause longer interruption to the > FIFO task due to execution of lower priority task > with very small sched slices). > > Commit d479960e44f27e0e52ba31b21740b703c538027c ("mm: disable LRU > pagevec during the migration temporarily") relies on > queueing work items on all online CPUs to ensure visibility > of lru_disable_count. > > However, its possible to use synchronize_rcu which will provide the same > guarantees (see comment this patch modifies on lru_cache_disable). > > Fixes: > > [ 1873.243925] INFO: task kworker/u160:0:9 blocked for more than 622 seconds. > [ 1873.243927] Tainted: G I --------- --- 5.14.0-31.rt21.31.el9.x86_64 #1 > [ 1873.243929] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1873.243929] task:kworker/u160:0 state:D stack: 0 pid: 9 ppid: 2 flags:0x00004000 > [ 1873.243932] Workqueue: cpuset_migrate_mm cpuset_migrate_mm_workfn > [ 1873.243936] Call Trace: > [ 1873.243938] __schedule+0x21b/0x5b0 > [ 1873.243941] schedule+0x43/0xe0 > [ 1873.243943] schedule_timeout+0x14d/0x190 > [ 1873.243946] ? resched_curr+0x20/0xe0 > [ 1873.243953] ? __prepare_to_swait+0x4b/0x70 > [ 1873.243958] wait_for_completion+0x84/0xe0 > [ 1873.243962] __flush_work.isra.0+0x146/0x200 > [ 1873.243966] ? flush_workqueue_prep_pwqs+0x130/0x130 > [ 1873.243971] __lru_add_drain_all+0x158/0x1f0 > [ 1873.243978] do_migrate_pages+0x3d/0x2d0 > [ 1873.243985] ? pick_next_task_fair+0x39/0x3b0 > [ 1873.243989] ? put_prev_task_fair+0x1e/0x30 > [ 1873.243992] ? pick_next_task+0xb30/0xbd0 > [ 1873.243995] ? __tick_nohz_task_switch+0x1e/0x70 > [ 1873.244000] ? raw_spin_rq_unlock+0x18/0x60 > [ 1873.244002] ? finish_task_switch.isra.0+0xc1/0x2d0 > [ 1873.244005] ? __switch_to+0x12f/0x510 > [ 1873.244013] cpuset_migrate_mm_workfn+0x22/0x40 > [ 1873.244016] process_one_work+0x1e0/0x410 > [ 1873.244019] worker_thread+0x50/0x3b0 > [ 1873.244022] ? process_one_work+0x410/0x410 > [ 1873.244024] kthread+0x173/0x190 > [ 1873.244027] ? set_kthread_struct+0x40/0x40 > [ 1873.244031] ret_from_fork+0x1f/0x30 > > Signed-off-by: Marcelo Tosatti Looks like great to me. Acked-by: Minchan Kim While I reviewed it, it seems I found a bug that br_lru_install needs to check lru_cache_disabled under bh_lru_lock. Let me cook the patch. Thanks!