From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout2.w1.samsung.com (mailout2.w1.samsung.com [210.118.77.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97CBF39B4BB for ; Tue, 7 Apr 2026 08:57:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.118.77.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775552245; cv=none; b=ShALgzzFDOj5j7+sjL3plxuEPdCkImQE0RSBt1W8iS4q8VecIccUW3/ajk2mx3WS5SJINt+7/sW1ZX8M9eV45KwQqVgozD5suzDg3ImkYw+S+zc3yxKkWroUMWPRTcW2NTJhvGxX0QrHmufmKLRKNpqtcErj6819uSEJKT2FywQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775552245; c=relaxed/simple; bh=flM5R4a3zc02/BOf48KzXgd1rgLMFNIw0OQjt1NUicI=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:In-Reply-To: Content-Type:References; b=JaoJAxnoi8ah/gxsNctF1elnJvNpHg2Ep34U9nndPK0SC68CsBxTtvHSpomwwLFNt+kUmHXd52DqRe3aasbKHpQMBpeMQvnO9bKf2wO8+QGIT38NoU0M1x374ON+QV44Revtup1oIi/HaBPlrrAIsxay3cmbtdld6oBFOERYG0A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=samsung.com; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b=RZP7wrMK; arc=none smtp.client-ip=210.118.77.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=samsung.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="RZP7wrMK" Received: from eucas1p2.samsung.com (unknown [182.198.249.207]) by mailout2.w1.samsung.com (KnoxPortal) with ESMTP id 20260407085713euoutp029bc79a26a29f7ebb521cf52d2a9098d4~kB1lYxSwU0422804228euoutp02X for ; Tue, 7 Apr 2026 08:57:13 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout2.w1.samsung.com 20260407085713euoutp029bc79a26a29f7ebb521cf52d2a9098d4~kB1lYxSwU0422804228euoutp02X DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1775552233; bh=j6bI40rFXjnNi4xEhtGuTS96Jn2uqw2dljQ1TolNlrY=; h=Date:From:Subject:To:Cc:In-Reply-To:References:From; b=RZP7wrMKzjWpTNSEshTsXiJTw8AOOP1zOFBBv3tS71vQiKtLXKVltuDeWF8EcIlfM zElp9QyxfncUuCiEwOUWl9FjZN1RcG+kB8hUgcqxg2h6EcoSs1h0Ivn4/iGzNp9W9Y Hbg61O3FN+HxRRDMyEpK+gegKhATJxWzq1dImPGc= Received: from eusmtip2.samsung.com (unknown [203.254.199.222]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20260407085713eucas1p2511c88350d65a30746d62a99c13306c5~kB1lHOMuj1628516285eucas1p2J; Tue, 7 Apr 2026 08:57:13 +0000 (GMT) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260407085711eusmtip2e1ec49f71f6ce486832315b6cf927c28~kB1jYPioW0291302913eusmtip27; Tue, 7 Apr 2026 08:57:11 +0000 (GMT) Message-ID: Date: Tue, 7 Apr 2026 10:57:10 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Betterbird (Windows) From: Marek Szyprowski Subject: Re: [PATCH v5 0/9] driver core: Fix some race conditions To: Douglas Anderson , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Alan Stern Cc: Leon Romanovsky , Christoph Hellwig , Robin Murphy , driver-core@lists.linux.dev, iommu@lists.linux.dev, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, linux-usb@vger.kernel.org, linux@armlinux.org.uk Content-Language: en-US In-Reply-To: <20260406232444.3117516-1-dianders@chromium.org> Content-Transfer-Encoding: 7bit X-CMS-MailID: 20260407085713eucas1p2511c88350d65a30746d62a99c13306c5 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260406232527eucas1p2faa678aa90f0636bd17e0a7f4cb8fa28 X-EPHeader: CA X-CMS-RootMailID: 20260406232527eucas1p2faa678aa90f0636bd17e0a7f4cb8fa28 References: <20260406232444.3117516-1-dianders@chromium.org> On 07.04.2026 01:22, Douglas Anderson wrote: > The main goal of this series is to fix the observed bug talked about > in the first patch ("driver core: Don't let a device probe until it's > ready"). That patch fixes a problem that has been observed in the real > world and could land even if the rest of the patches are found > unacceptable or need to be spun. > > That said, during patch review Danilo correctly pointed out that many > of the bitfield accesses in "struct device" are unsafe. I added a > bunch of patches in the series to address each one. > > Danilo said he's most worried about "can_match", so I put that one > first. After that, I tried to transition bitfields to flags in reverse > order to when the bitfield was added. > > Even if transitioning from bitfields to flags isn't truly needed for > correctness, it seems silly (and wasteful of space in struct device) > to have some in bitfields and some as flags. Thus I didn't spend time > for each bitfield showing that it's truly needed for correctness. > > Transition was done semi manually. Presumably someone skilled at > coccinelle could do a better job, but I just used sed in a heavy- > handed manner and then reviewed/fixed the results, undoing anything my > script got wrong. My terrible/ugly script was: > > var=can_match > caps="${var^^}" > for f in $(git grep -l "[>\.]${var}[^1-9_a-zA-Z\[]"); do > echo $f > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)->${var} = true/set_bit(DEV_FLAG_${caps}, \&\\1->flags)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)\.${var} = true/dev_set_${caps}(\&\\1)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)->${var} = false/clear_bit(DEV_FLAG_${caps}, \&\\1->flags)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)\.${var} = false/dev_clear_${caps}(\&\\1)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)->${var} = \([^;]*\)/assign_bit(DEV_FLAG_${caps}, \&\\1->flags, \\2)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)\.${var} = \([^;]*\)/dev_assign_${caps}(\&\\1, \\2)/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)->${var}\([^1-9_a-zA-Z\[]\)/test_bit(DEV_FLAG_${caps}, \&\\1->flags)\\2/" "$f" > sed -i~ -e "s/\([a-zA-Z_0-9\.>()-][a-zA-Z_0-9\.>()-]*\)\.${var}\([^1-9_a-zA-Z\[]\)/dev_${caps}(\&\\1)\\2/" "$f" > done > > From v3 to v4, I transitioned to accessor functions with another ugly > sed script. I had git format the old patches, then transformed them > with: > > for f in *.patch; do > echo $f > sed -i~ -e "s/test_and_set_bit(DEV_FLAG_\([^,]*\), \&\(.*\)->flags)/dev_test_and_set_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/test_and_set_bit(DEV_FLAG_\([^,]*\), \(.*\)\.flags)/dev_test_and_set_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/test_bit(DEV_FLAG_\([^,]*\), \&\(.*\)->flags)/dev_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/test_bit(DEV_FLAG_\([^,]*\), \(.*\)\.flags)/dev_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/set_bit(DEV_FLAG_\([^,]*\), \&\(.*\)->flags)/dev_set_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/set_bit(DEV_FLAG_\([^,]*\), \(.*\)\.flags)/dev_set_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/clear_bit(DEV_FLAG_\([^,]*\), \&\(.*\)->flags)/dev_clear_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/clear_bit(DEV_FLAG_\([^,]*\), \(.*\)\.flags)/dev_clear_\\L\\1(\\2)/" "$f" > sed -i~ -e "s/assign_bit(DEV_FLAG_\([^,]*\), \&\(.*\)->flags, \(.*\))/dev_assign_\\L\\1(\\2, \\3)/" "$f" > sed -i~ -e "s/assign_bit(DEV_FLAG_\([^,]*\), \(.*\)\.flags, \(.*\))/dev_assign_\\L\\1(\\2, \\3)/" "$f" > done > > ...and then did a few manual touchups for spacing. > > I only marked the first patch as a "Fix" since it is the only one > fixing observed problems. Other patches could be considered fixes too > if folks want. > > I tested the first patch in the series backported to kernel 6.6 on the > Pixel phone that was experiencing the race. I added extra printouts to > make sure that the problem was hitting / addressed. The rest of the > patches are tested with allmodconfig with arm32, arm64, ppc, and > x86. I boot tested on an arm64 Chromebook running mainline. The dma-mapping related bits are probably not race prone, but if you plan to refactor that part I won't object. Acked-by: Marek Szyprowski > Changes in v5: > - ready_to_prove => ready_to_probe typo > - device_lock() while calling dev_set_ready_to_probe() > - Add comment before "can_match = true" from Danilo. > - undef __create_dev_flag_accessors > > Changes in v4: > - Use accessor functions for flags > > Changes in v3: > - Use a new "flags" bitfield > - Add missing \n in probe error message > > Changes in v2: > - Instead of adjusting the ordering, use "ready_to_probe" flag > > Douglas Anderson (9): > driver core: Don't let a device probe until it's ready > driver core: Replace dev->can_match with dev_can_match() > driver core: Replace dev->dma_iommu with dev_dma_iommu() > driver core: Replace dev->dma_skip_sync with dev_dma_skip_sync() > driver core: Replace dev->dma_ops_bypass with dev_dma_ops_bypass() > driver core: Replace dev->state_synced with dev_state_synced() > driver core: Replace dev->dma_coherent with dev_dma_coherent() > driver core: Replace dev->of_node_reused with dev_of_node_reused() > driver core: Replace dev->offline + ->offline_disabled with accessors > > arch/arc/mm/dma.c | 4 +- > arch/arm/mach-highbank/highbank.c | 2 +- > arch/arm/mach-mvebu/coherency.c | 2 +- > arch/arm/mm/dma-mapping-nommu.c | 4 +- > arch/arm/mm/dma-mapping.c | 28 ++-- > arch/arm64/kernel/cpufeature.c | 2 +- > arch/arm64/mm/dma-mapping.c | 2 +- > arch/mips/mm/dma-noncoherent.c | 2 +- > arch/powerpc/kernel/dma-iommu.c | 8 +- > .../platforms/pseries/hotplug-memory.c | 4 +- > arch/riscv/mm/dma-noncoherent.c | 2 +- > drivers/acpi/scan.c | 2 +- > drivers/base/core.c | 55 +++++--- > drivers/base/cpu.c | 4 +- > drivers/base/dd.c | 36 ++++-- > drivers/base/memory.c | 2 +- > drivers/base/pinctrl.c | 2 +- > drivers/base/platform.c | 2 +- > drivers/dma/ti/k3-udma-glue.c | 6 +- > drivers/dma/ti/k3-udma.c | 6 +- > drivers/iommu/dma-iommu.c | 9 +- > drivers/iommu/iommu.c | 5 +- > drivers/net/pcs/pcs-xpcs-plat.c | 2 +- > drivers/of/device.c | 6 +- > drivers/pci/of.c | 2 +- > drivers/pci/pwrctrl/core.c | 2 +- > drivers/regulator/bq257xx-regulator.c | 2 +- > drivers/regulator/rk808-regulator.c | 2 +- > drivers/tty/serial/serial_base_bus.c | 2 +- > drivers/usb/gadget/udc/aspeed-vhub/dev.c | 2 +- > include/linux/device.h | 122 ++++++++++++------ > include/linux/dma-map-ops.h | 6 +- > include/linux/dma-mapping.h | 2 +- > include/linux/iommu-dma.h | 3 +- > kernel/cpu.c | 4 +- > kernel/dma/mapping.c | 12 +- > mm/hmm.c | 2 +- > 37 files changed, 218 insertions(+), 142 deletions(-) > Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland