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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 9B70BC2D0CE for ; Fri, 3 Jan 2020 18:33:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3BEFE222C3 for ; Fri, 3 Jan 2020 18:33:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QGC5fugM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3BEFE222C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8A18D8E0005; Fri, 3 Jan 2020 13:33:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 829498E0003; Fri, 3 Jan 2020 13:33:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F16B8E0005; Fri, 3 Jan 2020 13:33:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0056.hostedemail.com [216.40.44.56]) by kanga.kvack.org (Postfix) with ESMTP id 56F418E0003 for ; Fri, 3 Jan 2020 13:33:19 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id ECC0A180AD801 for ; Fri, 3 Jan 2020 18:33:18 +0000 (UTC) X-FDA: 76337170476.03.toad75_39fe35daa8f4b X-HE-Tag: toad75_39fe35daa8f4b X-Filterd-Recvd-Size: 6581 Received: from mail-oi1-f195.google.com (mail-oi1-f195.google.com [209.85.167.195]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jan 2020 18:33:18 +0000 (UTC) Received: by mail-oi1-f195.google.com with SMTP id c16so14796101oic.3 for ; Fri, 03 Jan 2020 10:33:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=A2J/z9YCgqSFZkvmrAHk+G44mHEtBjhodDjeUyPIRHs=; b=QGC5fugMG0Gs0vEivA/3nS4doTtmK7k8njJd2psM357QzWLRAymxFYo8EllWi2Qu+i vAPQdvwdKmEkt9Zj9fkZ6F61SA75LUKl6JDozDWbL7kfn7sdzgRivJwgp7ijbAn6j+OS M2kxLp3LIK0k1KJ+lowLb2MvbZBzk4fyN6ad/IXpYaD/i++Hg5wrSSCtJFVo4yIhn6RY mz/7iL+TMKMugVfcyRPd02lby4rSqmxvUeURNc0GdKJJUqr8VDfiIDv03bmccf8vVmpP bxaiXtqaWs9G54XfTFNR7+rsldg8lfj3449++8xqO++jyIQHZFA+D2mxBLBB1BRWESXr 6VvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=A2J/z9YCgqSFZkvmrAHk+G44mHEtBjhodDjeUyPIRHs=; b=Zq2PsGbz00CJVRP3jIWNYOQZA+ooOHEHwhd/7fI/q8k1upXr58rQ+xOC5Tp6jWzlZk js33teIaZrJ+84B5wIPQqAMJtaZs6TEoh1Urff07zs05svI0+ZuXZeM3DHXJq+a04Qdy OFkff7A2y+D5jTl7FzkHFnj1SUFF9eESuSfJ5q25AIJJNwo88uDCW8X3lFBPiGhKoW/U zusOK4KcPSVuviz+klBFxhOz6hy9PDjsjC/n6NIH3QsOLRtlA6JUjuZMYLMgASCcTnbq SOYkkXHWL8UgYwr6hyYuxjbOte5Dej6R1JSPQxrfmgKxGpszCYYHbVo7/sUls7Hd7a7M hFXw== X-Gm-Message-State: APjAAAU2O1ozrVwinbhfqVoe9vSxmwJkqA4H4tAsL6mntiMC6JVhI6oF JLo2iJP1b7Ud3VCrofsQs/8R3yTnH2xO1A0c95+8jA== X-Google-Smtp-Source: APXvYqxXWtd8gakw2WXfkITo98Pyway1XHzMFBzyHenstxRt7/wVREBiyQRe52VrVgjmQ4BKesvpHAImYmiTAzYZhjE= X-Received: by 2002:a05:6808:64e:: with SMTP id z14mr4308580oih.79.1578076397272; Fri, 03 Jan 2020 10:33:17 -0800 (PST) MIME-Version: 1.0 References: <20200103085503.1665-1-ahuang12@lenovo.com> In-Reply-To: <20200103085503.1665-1-ahuang12@lenovo.com> From: Shakeel Butt Date: Fri, 3 Jan 2020 10:33:05 -0800 Message-ID: Subject: Re: [PATCH 1/1] mm: memcg/slab: Call flush_memcg_workqueue() only if memcg workqueue is valid To: Adrian Huang Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Linux MM , Adrian Huang , Joerg Roedel Content-Type: text/plain; charset="UTF-8" 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 Fri, Jan 3, 2020 at 12:55 AM Adrian Huang wrote: > > From: Adrian Huang > > When booting with amd_iommu=off, the following WARNING message > appears: > AMD-Vi: AMD IOMMU disabled on kernel command-line > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 0 at kernel/workqueue.c:2772 flush_workqueue+0x42e/0x450 > Modules linked in: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.5.0-rc3-amd-iommu #6 > Hardware name: Lenovo ThinkSystem SR655-2S/7D2WRCZ000, BIOS D8E101L-1.00 12/05/2019 > RIP: 0010:flush_workqueue+0x42e/0x450 > Code: ff 0f 0b e9 7a fd ff ff 4d 89 ef e9 33 fe ff ff 0f 0b e9 7f fd ff ff 0f 0b e9 bc fd ff ff 0f 0b e9 a8 fd ff ff e8 52 2c fe ff <0f> 0b 31 d2 48 c7 c6 e0 88 c5 95 48 c7 c7 d8 ad f0 95 e8 19 f5 04 > RSP: 0000:ffffffff96203d80 EFLAGS: 00010246 > RAX: ffffffff96203dc8 RBX: 0000000000000000 RCX: 0000000000000000 > RDX: ffffffff96a63120 RSI: ffffffff95efcba2 RDI: ffffffff96203dc0 > RBP: ffffffff96203e08 R08: 0000000000000000 R09: ffffffff962a1828 > R10: 00000000f0000080 R11: dead000000000100 R12: ffff8d8a87c0a770 > R13: dead000000000100 R14: 0000000000000456 R15: ffffffff96203da0 > FS: 0000000000000000(0000) GS:ffff8d8dbd000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff8d91cfbff000 CR3: 000000078920a000 CR4: 00000000000406b0 > Call Trace: > ? wait_for_completion+0x51/0x180 > kmem_cache_destroy+0x69/0x260 > iommu_go_to_state+0x40c/0x5ab > amd_iommu_prepare+0x16/0x2a > irq_remapping_prepare+0x36/0x5f > enable_IR_x2apic+0x21/0x172 > default_setup_apic_routing+0x12/0x6f > apic_intr_mode_init+0x1a1/0x1f1 > x86_late_time_init+0x17/0x1c > start_kernel+0x480/0x53f > secondary_startup_64+0xb6/0xc0 > ---[ end trace 30894107c3749449 ]--- > x2apic: IRQ remapping doesn't support X2APIC mode > x2apic disabled > > The warning is caused by the calling of 'kmem_cache_destroy()' > in free_iommu_resources(). Here is the call path: > free_iommu_resources > kmem_cache_destroy > flush_memcg_workqueue > flush_workqueue > > The root cause is that the IOMMU subsystem runs before the > workqueue subsystem, which the variable 'wq_online' is still 'false'. > This leads to the statement 'if (WARN_ON(!wq_online))' in > flush_workqueue() is 'true'. > > Since the variable 'memcg_kmem_cache_wq' is not allocated > during the time, it is unnecessary to call flush_memcg_workqueue(). > This prevents the WARNING message triggered by flush_workqueue(). > > Cc: Shakeel Butt > Cc: Joerg Roedel > Reported-by: Xiaochun Lee > Signed-off-by: Adrian Huang Fixes: 92ee383f6daab ("mm: fix race between kmem_cache destroy, create and deactivate") Reviewed-by: Shakeel Butt Should this be backported to stable trees? > --- > mm/slab_common.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index f0ab6d4ceb4c..0d95ddea13b0 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -903,7 +903,8 @@ static void flush_memcg_workqueue(struct kmem_cache *s) > * deactivates the memcg kmem_caches through workqueue. Make sure all > * previous workitems on workqueue are processed. > */ > - flush_workqueue(memcg_kmem_cache_wq); > + if (likely(memcg_kmem_cache_wq)) > + flush_workqueue(memcg_kmem_cache_wq); > > /* > * If we're racing with children kmem_cache deactivation, it might > -- > 2.17.1 >