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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1C4CC54EE9 for ; Tue, 20 Sep 2022 07:46:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 250B7940008; Tue, 20 Sep 2022 03:46:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 200B1940007; Tue, 20 Sep 2022 03:46:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F02B940008; Tue, 20 Sep 2022 03:46:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id F3C78940007 for ; Tue, 20 Sep 2022 03:46:48 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id CB7B5AB0CB for ; Tue, 20 Sep 2022 07:46:48 +0000 (UTC) X-FDA: 79931682096.08.B37D8E0 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) by imf27.hostedemail.com (Postfix) with ESMTP id 7422D40002 for ; Tue, 20 Sep 2022 07:46:48 +0000 (UTC) Received: by mail-pj1-f44.google.com with SMTP id i15-20020a17090a4b8f00b0020073b4ac27so1625901pjh.3 for ; Tue, 20 Sep 2022 00:46:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=ofrSUBwHj0NfDL7/4OpZdl7qygj1PrA532lfio/4jhs=; b=lkta8/dweehjY5XgTHqsJY/c32ELVi2VUyZSArZvWkZuX4xoZ88CWuhTlWQt4EB5eG fkIbTGqleHmkSpRlq6jii/oglIsxigMJA4BkqhDDTGxliCEkOW4K7qW8bDZxW4xNdURx x9/SKwq51qzeBYQ73kS2n9DQ4hFL9JrCggratIkxtr2CjbZFqnon+CfbszyNHwsnBi0g RLoACY0fL0QmBDyCgh3PLBAEFBAdpRE9o8vVUIyDP4c/GgwE4tn+zdDwKuXYTFy8SPV6 eVxEywuyzViONLK3Id4u8+kq1H2nAQ8otvnPQcEgIH6M6XAzPg6DHtm8t2zlIXhLdByU PfVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=ofrSUBwHj0NfDL7/4OpZdl7qygj1PrA532lfio/4jhs=; b=NzbkFClUQbH6amxVYMGqqWu+konbpnbhcosTFXOPB1VW6MZIVszTmM17WYiusC4ECr H9JM7Xpvr/kjV7Yu+NLm6FuVjnZkaWsL2yvg3mXczl+ggN2q6bI2+yf1p0vsIudBqplV zaBj/ohL9MP8sru09D+nsO6zmMErXHGzHpPKckOvMLVSS4gtTqTZL1+W5EjxbeVkBsfO AqQRE5fsjSR4LddA7mnLc7mh7dmnt8ePB1B2sVD89vdrauUyWYHHYNqf2CaXxpB7lye2 g7V8IyNaqwhgtFIaVE/l3+XdrCZ+eTG9O7sqcLK8n7eE9soivB8P/ZKhVaeYUosRZbhi yeUQ== X-Gm-Message-State: ACrzQf0aWXbTr+4i4M7KyuY46q52aQbMPPt5U/1pGrb0VcwkQLTGGgau YkFJAB6zNpG4Cl+VjW4PvRtba2RJSvg= X-Google-Smtp-Source: AMsMyM4d/TkqJTxG4OlN7aA8vCeRP9ueZ1ErnhTr0ulMBWNQRksrIvXzDEASXZcz16CmyCLfYOC4vg== X-Received: by 2002:a17:90b:4b03:b0:202:eab3:e174 with SMTP id lx3-20020a17090b4b0300b00202eab3e174mr2456851pjb.12.1663660007365; Tue, 20 Sep 2022 00:46:47 -0700 (PDT) Received: from hyeyoo ([114.29.91.56]) by smtp.gmail.com with ESMTPSA id c12-20020a17090aa60c00b001fd8316db51sm755689pjq.7.2022.09.20.00.46.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Sep 2022 00:46:46 -0700 (PDT) Date: Tue, 20 Sep 2022 16:46:41 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Maurizio Lombardi Cc: vbabka@suse.cz, linux-mm@kvack.org, rientjes@google.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, bigeasy@linutronix.de Subject: Re: [PATCH V3] mm: slub: fix flush_cpu_slab()/__free_slab() invocations in task context. Message-ID: References: <20220919163929.351068-1-mlombard@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220919163929.351068-1-mlombard@redhat.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663660008; a=rsa-sha256; cv=none; b=vZC1u24AJRWJ7Ax8UVVE4GdDmjF87ozXcm0ZZn5lp49mSf22UG6UtrKy+yHgucHenyiTn9 cY0cb3xyY36j6zrWPgjs+aTXxtGWBZOB5+4fcxyHbJhJ4Jqs3wjJinqwPf8XAO412LVFxZ +nPYBRlQBfi8roHmiuyxHl/Tjj/kB5g= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="lkta8/dw"; spf=pass (imf27.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.44 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663660008; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ofrSUBwHj0NfDL7/4OpZdl7qygj1PrA532lfio/4jhs=; b=Yzt38Yz59/vg/nsLJVNnfuFfNGXkuxlzrID2JyoHpd4Ei+IAMeCshav5mCoVllOJj435YJ RZj+JPh+y5agYMHBfr9mO7zHM7mvm8gn2MHDjaDgr0ChP0V1qOJrhHtfropNaeqjWyxj9t t/Zgo+4oFQmkxtet49CKmTdZmKSQmhY= X-Stat-Signature: 3kz1zb9w9enkdarktmhxo74suzq8dnwb X-Rspamd-Queue-Id: 7422D40002 Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="lkta8/dw"; spf=pass (imf27.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.44 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1663660008-137399 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Sep 19, 2022 at 06:39:29PM +0200, Maurizio Lombardi wrote: > Commit 5a836bf6b09f ("mm: slub: move flush_cpu_slab() invocations > __free_slab() invocations out of IRQ context") moved all flush_cpu_slab() > invocations to the global workqueue to avoid a problem related > with deactivate_slab()/__free_slab() being called from an IRQ context > on PREEMPT_RT kernels. > > When the flush_all_cpu_locked() function is called from a task context > it may happen that a workqueue with WQ_MEM_RECLAIM bit set ends up > flushing the global workqueue, this will cause a dependency issue. > > workqueue: WQ_MEM_RECLAIM nvme-delete-wq:nvme_delete_ctrl_work [nvme_core] > is flushing !WQ_MEM_RECLAIM events:flush_cpu_slab > WARNING: CPU: 37 PID: 410 at kernel/workqueue.c:2637 > check_flush_dependency+0x10a/0x120 > Workqueue: nvme-delete-wq nvme_delete_ctrl_work [nvme_core] > RIP: 0010:check_flush_dependency+0x10a/0x120[ 453.262125] Call Trace: > __flush_work.isra.0+0xbf/0x220 > ? __queue_work+0x1dc/0x420 > flush_all_cpus_locked+0xfb/0x120 > __kmem_cache_shutdown+0x2b/0x320 > kmem_cache_destroy+0x49/0x100 > bioset_exit+0x143/0x190 > blk_release_queue+0xb9/0x100 > kobject_cleanup+0x37/0x130 > nvme_fc_ctrl_free+0xc6/0x150 [nvme_fc] > nvme_free_ctrl+0x1ac/0x2b0 [nvme_core] > > Fix this bug by creating a workqueue for the flush operation with > the WQ_MEM_RECLAIM bit set. > > v2: Create a workqueue with WQ_MEM_RECLAIM > instead of trying to revert the changes. > > v3: replace create_workqueue() with alloc_workqueue() and BUG_ON() with > WARN_ON() > > Signed-off-by: Maurizio Lombardi > --- > mm/slub.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 862dbd9af4f5..016da09608fb 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -310,6 +310,11 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si) > */ > static nodemask_t slab_nodes; > > +/* > + * Workqueue used for flush_cpu_slab(). > + */ > +static struct workqueue_struct *flushwq; > + > /******************************************************************** > * Core slab cache functions > *******************************************************************/ > @@ -2730,7 +2735,7 @@ static void flush_all_cpus_locked(struct kmem_cache *s) > INIT_WORK(&sfw->work, flush_cpu_slab); > sfw->skip = false; > sfw->s = s; > - schedule_work_on(cpu, &sfw->work); > + queue_work_on(cpu, flushwq, &sfw->work); Hi. what happens here if flushwq failed? I think avoiding BUG_ON() makes sense, but shouldn't we have fallback method? > } > > for_each_online_cpu(cpu) { > @@ -4858,6 +4863,8 @@ void __init kmem_cache_init(void) > > void __init kmem_cache_init_late(void) > { > + flushwq = alloc_workqueue("slub_flushwq", WQ_MEM_RECLAIM, 0); > + WARN_ON(!flushwq); > } > > struct kmem_cache * > -- > 2.31.1 > > -- Thanks, Hyeonggon