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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CD1BC433EF for ; Tue, 19 Oct 2021 21:13:39 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 683A360174 for ; Tue, 19 Oct 2021 21:13:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 683A360174 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=znWccsQ6V+daZ+fQequ1z2c6tPH0Gy7H2VVwI5ZSMAM=; b=zNbZpgKrs3gM7L Eq7vXnT/buJ5WQbNrJdEv2qrKKQlYs764oo1XZRE6beILWTEZt5xQldP0s4ZLXnOLi+UmYut/vWP/ dwWfWtH3D2t6uZ77a3QEzvYUF9n+SiJLR+MH2J4dCIxZ5MjRO8xp2dn2jyIqK0XWXdJKHiTgUZLXC wlmJUWkYEBliCqfeZPrwvjk3inpMkiz+BMbRkTrmxfAX/hNN6fU1uJmaikRopFDad6mWK1GhxMJwH zFhwzF+mj/vY9rMNEHylIlTbq2hCcFqbMBhelwVRyHCQ28t5vc0kMCXR4zeA+fBAY+ngyXOgdBrhJ sBuXfwoRgdY3dZdGnaNg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mcwOi-002eYf-9b; Tue, 19 Oct 2021 21:11:48 +0000 Received: from mail-ed1-x529.google.com ([2a00:1450:4864:20::529]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mcwOd-002eX1-Ta for linux-arm-kernel@lists.infradead.org; Tue, 19 Oct 2021 21:11:45 +0000 Received: by mail-ed1-x529.google.com with SMTP id ec8so18167075edb.6 for ; Tue, 19 Oct 2021 14:11:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=OwyRLUcszsyadBr824dsTniinvYZj7Tk0bJGgvItSRM=; b=UuFOxeYnA6bmCHsx6C3eM8RhW7dy8MiborwVIsDzXcWw30k69JKWDiVtNm6tzfQYNS jKiqu/iSWMz34Bs26vA6cuq5v9Mmweone0oANMssKmhBtWARTGXALWfHR+h8jbZ8pvcy 0krFAiUyPTdfBf/P4H/lPhWeu8aOt+4rtcYRs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :content-transfer-encoding:in-reply-to; bh=OwyRLUcszsyadBr824dsTniinvYZj7Tk0bJGgvItSRM=; b=PjHR9Ize0rg6Ka3LYIf+di6ObgeQdB+dlGotd6GU5KZR0GARfQMwwcz3KrFrpjhEC5 8OhnE+C00PHCH11CuZ2RtYCNjycR4hTFQCn7qCCSynC5N5zMnhFtMZ/ns5u/Smq2wFV6 50WIkrUPi2qDh89oD0gA+hmwVaxqwJlvCX0dgEY/SaWB6ukx7CzLM77/8gue/Ij3Hc6U qhPxoPHXZTaLNtTWv1WgU6xFV981iuPAdZVCNfVz9tyqF++a0oufk5Dx8eVNEeNiu8AF b9tFZPssO8Sc+lQl+Yx0+vm1nncxlVJmgQrr1b+I/j7e3eUUgoPSGQOkjWcWTF/8Nvye Ob9Q== X-Gm-Message-State: AOAM530gNymqQCY2VZSNaKLLHeJ4Jwv8xiF6A0DiYbUnr64lZrNmKoLc gJp9eEvXoge7ZbyVO3wzL4FGLQ== X-Google-Smtp-Source: ABdhPJxVcAFeCcFJ0BV5iO1FeaZa+XJFmc7PEYU7imdaPNyCQNJYbrUDecQv4qxDFiRydF4XQvCUaw== X-Received: by 2002:a05:6402:2787:: with SMTP id b7mr56873542ede.159.1634677899626; Tue, 19 Oct 2021 14:11:39 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id q14sm92905edj.42.2021.10.19.14.11.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Oct 2021 14:11:39 -0700 (PDT) Date: Tue, 19 Oct 2021 23:11:37 +0200 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: guangming.cao@mediatek.com, Sumit Semwal , Christian =?iso-8859-1?Q?K=F6nig?= , Matthias Brugger , "open list:DMA BUFFER SHARING FRAMEWORK" , "open list:DMA BUFFER SHARING FRAMEWORK" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , open list , "moderated list:ARM/Mediatek SoC support" , "moderated list:ARM/Mediatek SoC support" , wsd_upstream@mediatek.com Subject: Re: [Linaro-mm-sig] [PATCH] dma-buf: add attachments empty check for dma_buf_release Message-ID: Mail-Followup-To: Christian =?iso-8859-1?Q?K=F6nig?= , guangming.cao@mediatek.com, Sumit Semwal , Christian =?iso-8859-1?Q?K=F6nig?= , Matthias Brugger , "open list:DMA BUFFER SHARING FRAMEWORK" , "open list:DMA BUFFER SHARING FRAMEWORK" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , open list , "moderated list:ARM/Mediatek SoC support" , "moderated list:ARM/Mediatek SoC support" , wsd_upstream@mediatek.com References: <20211019122345.160555-1-guangming.cao@mediatek.com> <8cca7188-6484-d3a5-2b87-400f6500e742@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <8cca7188-6484-d3a5-2b87-400f6500e742@gmail.com> X-Operating-System: Linux phenom 5.10.0-8-amd64 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211019_141143_971768_333AFE26 X-CRM114-Status: GOOD ( 39.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 19, 2021 at 05:37:27PM +0200, Christian K=F6nig wrote: > = > = > Am 19.10.21 um 14:41 schrieb Daniel Vetter: > > On Tue, Oct 19, 2021 at 08:23:45PM +0800, guangming.cao@mediatek.com wr= ote: > > > From: Guangming Cao > > > = > > > Since there is no mandatory inspection for attachments in dma_buf_rel= ease. > > > There will be a case that dma_buf already released but attachment is = still > > > in use, which can points to the dmabuf, and it maybe cause > > > some unexpected issues. > > > = > > > With IOMMU, when this cases occurs, there will have IOMMU address > > > translation fault(s) followed by this warning, > > > I think it's useful for dma devices to debug issue. > > > = > > > Signed-off-by: Guangming Cao > > This feels a lot like hand-rolling kobject debugging. If you want to do > > this then I think adding kobject debug support to > > dma_buf/dma_buf_attachment would be better than hand-rolling something > > bespoke here. > = > Well I would call that overkill. I think if done right the object debug stuff should be able to give you a backtrace. Which might be useful if you have a dma-buf heaps design where you really have no clue why a buffer was allocated/attached without some hints. > > Also on the patch itself: You don't need the trylock. For correctly > > working code non one else can get at the dma-buf, so no locking needed = to > > iterate through the attachment list. For incorrect code the kernel will= be > > on fire pretty soon anyway, trying to do locking won't help :-) And > > without the trylock we can catch more bugs (e.g. if you also forgot to > > unlock and not just forgot to detach). > = > You also don't need the WARN(!list_empty...) because a few line below we > already have a "WARN_ON(!list_empty(&dmabuf->attachments));". Yeah this patch here alone isn't really that useful I think. Maybe we could add the dmabuf->exp_name or so to that warning, but otherwise the info printed here isn't all that useful for debugging. Grabbing a backtrace of the allocator or attacher otoh should fairly immedialy point at the buggy code. -Daniel > = > Christian. > = > > -Daniel > > = > > > --- > > > drivers/dma-buf/dma-buf.c | 23 +++++++++++++++++++++++ > > > 1 file changed, 23 insertions(+) > > > = > > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > > > index 511fe0d217a0..672404857d6a 100644 > > > --- a/drivers/dma-buf/dma-buf.c > > > +++ b/drivers/dma-buf/dma-buf.c > > > @@ -74,6 +74,29 @@ static void dma_buf_release(struct dentry *dentry) > > > */ > > > BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active); > > > + /* attachment check */ > > > + if (dma_resv_trylock(dmabuf->resv) && WARN(!list_empty(&dmabuf->att= achments), > > > + "%s err, inode:%08lu size:%08zu name:%s exp_name:%s flags:0x%08= x mode:0x%08x, %s\n", > > > + __func__, file_inode(dmabuf->file)->i_ino, dmabuf->size, > > > + dmabuf->name, dmabuf->exp_name, > > > + dmabuf->file->f_flags, dmabuf->file->f_mode, > > > + "Release dmabuf before detach all attachments, dump attach:\n")= ) { > > > + int attach_cnt =3D 0; > > > + dma_addr_t dma_addr; > > > + struct dma_buf_attachment *attach_obj; > > > + /* dump all attachment info */ > > > + list_for_each_entry(attach_obj, &dmabuf->attachments, node) { > > > + dma_addr =3D (dma_addr_t)0; > > > + if (attach_obj->sgt) > > > + dma_addr =3D sg_dma_address(attach_obj->sgt->sgl); > > > + pr_err("attach[%d]: dev:%s dma_addr:0x%-12lx\n", > > > + attach_cnt, dev_name(attach_obj->dev), dma_addr); > > > + attach_cnt++; > > > + } > > > + pr_err("Total %d devices attached\n\n", attach_cnt); > > > + dma_resv_unlock(dmabuf->resv); > > > + } > > > + > > > dmabuf->ops->release(dmabuf); > > > if (dmabuf->resv =3D=3D (struct dma_resv *)&dmabuf[1]) > > > -- = > > > 2.17.1 > > > = > = -- = Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel