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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 069BDC43460 for ; Tue, 27 Apr 2021 12:41:23 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 9D33E613BD for ; Tue, 27 Apr 2021 12:41:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D33E613BD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 467E0607EB; Tue, 27 Apr 2021 12:41:22 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id egBKBeUs4xeL; Tue, 27 Apr 2021 12:41:20 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp3.osuosl.org (Postfix) with ESMTP id 2422F607C0; Tue, 27 Apr 2021 12:41:20 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id EEC9AC000E; Tue, 27 Apr 2021 12:41:19 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 77227C000B for ; Tue, 27 Apr 2021 12:41:19 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 65F5183BF2 for ; Tue, 27 Apr 2021 12:41:19 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp1.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=linuxfoundation.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9fFQhzsdkcB9 for ; Tue, 27 Apr 2021 12:41:18 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp1.osuosl.org (Postfix) with ESMTPS id 53BA083BE0 for ; Tue, 27 Apr 2021 12:41:18 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 457B861059; Tue, 27 Apr 2021 12:41:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619527277; bh=P+oLcg/KgUKwLIvYmcCRqckymcvWUs4EWrMcpfr89qA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Si+4HW3ASVsCkRRhUXpnUKiBsIwvgH3s6gMg4zAZtzXEBMAmchfr006GslZOmi5ne zmyRrYlPnFg9Gj9jQ+zSQi0qCfjzk2AUWbN6rWwfgbhACVw4/Ibky3v05fZ2wOybUi aCGmRnJQGAhbBdGCJVlGikWmDcmXUoCL4vLwa3EQ= Date: Tue, 27 Apr 2021 14:41:15 +0200 From: Greg KH To: Robin Murphy Subject: Re: dma-api debugfs directory is not created since debugfs is not initialized Message-ID: References: <22f268bb-9b96-1208-0292-68c9b50422a1@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <22f268bb-9b96-1208-0292-68c9b50422a1@arm.com> Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Corentin Labbe , hch@lst.de X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Apr 27, 2021 at 01:32:50PM +0100, Robin Murphy wrote: > On 2021-04-27 12:39, Greg KH wrote: > > On Tue, Apr 27, 2021 at 01:34:27PM +0200, Corentin Labbe wrote: > > > Hello > > > > > > I try to debug some DMA problem on next-20210427, and so I have enabled CONFIG_DMA_API_DEBUG=y. > > > But the dma-api directory does show up in debugfs, but lot of other directory exists in it. > > > > Does it show up properly in 5.12? > > > > > After debugging it seems due to commit 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized") > > > Reverting the commit permit to "dma-api" debugfs to be found. (but seems not the right way to fix it). > > > > We have had some odd start-up ordering issues that the above commit has > > caused to show. Given that this commit is now in stable kernels, with > > no report of this issue so far, I'm worried that maybe this is a dma > > subsystem ordering issue? > > Both debugfs_init() and dma_debug_init() do run at core_initcall level, and > disassembling the vmlinux from my current working tree does indeed suggest > that they somehow end up in the wrong relative order: > > [...] > ffff80001160d0c8 <__initcall__kmod_debug__325_918_dma_debug_init1>: > ffff80001160d0c8: feb0d528 .word 0xfeb0d528 > > [...] > > ffff80001160d108 <__initcall__kmod_debugfs__357_848_debugfs_init1>: > ffff80001160d108: fff4326c .word 0xfff4326c > [...] > > > I always had the impression that initcall ordering tended to work out > roughly alphabetical, such that entries from fs/* might come before > kernel/*, but I guess it's at the whims of the linker in the end :/ init call ordering happens from link ordering. > Perhaps the easiest thing to do is split out dma_debug_fs_init() and run > that at a later level? We do want the dma-debug infrastructure itself to be > up as early as possible, but I think the debugfs view of its internals can > happily wait until closer to the time that there's actually a userspace to > be able to look at it. That seems like a better idea here, there's no need for "special treatment" of debugfs. thanks, greg k-h _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu