[{"id":3673486,"web_url":"http://patchwork.ozlabs.org/comment/3673486/","msgid":"","date":"2026-04-04T17:11:59","subject":"Re: [PATCH v4 0/9] driver core: Fix some race conditions","submitter":{"id":64267,"url":"http://patchwork.ozlabs.org/api/people/64267/","name":"Rafael J. Wysocki","email":"rafael@kernel.org"},"content":"On Sat, Apr 4, 2026 at 2:07 AM Douglas Anderson wrote:\n>\n> The main goal of this series is to fix the observed bug talked about\n> in the first patch (\"driver core: Don't let a device probe until it's\n> ready\"). That patch fixes a problem that has been observed in the real\n> world and could land even if the rest of the patches are found\n> unacceptable or need to be spun.\n>\n> That said, during patch review Danilo correctly pointed out that many\n> of the bitfield accesses in \"struct device\" are unsafe. I added a\n> bunch of patches in the series to address each one.\n>\n> Danilo said he's most worried about \"can_match\", so I put that one\n> first. After that, I tried to transition bitfields to flags in reverse\n> order to when the bitfield was added.\n>\n> Even if transitioning from bitfields to flags isn't truly needed for\n> correctness, it seems silly (and wasteful of space in struct device)\n> to have some in bitfields and some as flags. Thus I didn't spend time\n> for each bitfield showing that it's truly needed for correctness.\n>\n> Transition was done semi manually. Presumably someone skilled at\n> coccinelle could do a better job, but I just used sed in a heavy-\n> handed manner and then reviewed/fixed the results, undoing anything my\n> script got wrong. My terrible/ugly script was:\n>\n> var=can_match\n> caps=\"${var^^}\"\n> for f in $(git grep -l \"[>\\.]${var}[^1-9_a-zA-Z\\[]\"); do\n> echo $f\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)->${var} = true/set_bit(DEV_FLAG_${caps}, \\&\\\\1->flags)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)\\.${var} = true/dev_set_${caps}(\\&\\\\1)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)->${var} = false/clear_bit(DEV_FLAG_${caps}, \\&\\\\1->flags)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)\\.${var} = false/dev_clear_${caps}(\\&\\\\1)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)->${var} = \\([^;]*\\)/assign_bit(DEV_FLAG_${caps}, \\&\\\\1->flags, \\\\2)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)\\.${var} = \\([^;]*\\)/dev_assign_${caps}(\\&\\\\1, \\\\2)/\" \"$f\"\n> sed -i~ -e \"s/\\([a-zA-Z_0-9\\.>()-][a-zA-Z_0-9\\.>()-]*\\)->${var}\\([^1-9_a-zA-Z\\[]\\)/test_bit(DEV_FLAG_${caps}, \\&\\\\1->flags)\\\\2/\" \"$f\"\n> 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\"\n> done\n>\n> From v3 to v4, I transitioned to accessor functions with another ugly\n> sed script. I had git format the old patches, then transformed them\n> with:\n>\n> for f in *.patch; do\n> echo $f\n> sed -i~ -e \"s/test_and_set_bit(DEV_FLAG_\\([^,]*\\), \\&\\(.*\\)->flags)/dev_test_and_set_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/test_and_set_bit(DEV_FLAG_\\([^,]*\\), \\(.*\\)\\.flags)/dev_test_and_set_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/test_bit(DEV_FLAG_\\([^,]*\\), \\&\\(.*\\)->flags)/dev_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/test_bit(DEV_FLAG_\\([^,]*\\), \\(.*\\)\\.flags)/dev_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/set_bit(DEV_FLAG_\\([^,]*\\), \\&\\(.*\\)->flags)/dev_set_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/set_bit(DEV_FLAG_\\([^,]*\\), \\(.*\\)\\.flags)/dev_set_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/clear_bit(DEV_FLAG_\\([^,]*\\), \\&\\(.*\\)->flags)/dev_clear_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/clear_bit(DEV_FLAG_\\([^,]*\\), \\(.*\\)\\.flags)/dev_clear_\\\\L\\\\1(\\\\2)/\" \"$f\"\n> sed -i~ -e \"s/assign_bit(DEV_FLAG_\\([^,]*\\), \\&\\(.*\\)->flags, \\(.*\\))/dev_assign_\\\\L\\\\1(\\\\2, \\\\3)/\" \"$f\"\n> sed -i~ -e \"s/assign_bit(DEV_FLAG_\\([^,]*\\), \\(.*\\)\\.flags, \\(.*\\))/dev_assign_\\\\L\\\\1(\\\\2, \\\\3)/\" \"$f\"\n> done\n>\n> ...and then did a few manual touchups for spacing.\n>\n> NOTE: one potentially \"controversial\" choice I made in some patches\n> was to always reserve a flag ID even if a flag is only used under\n> certain CONFIG_ settings. This is a change from how things were\n> before. Keeping the numbering consistent and allowing easy\n> compile-testing of both CONFIG settings seemed worth it, especially\n> since it won't take up any extra space until we've added a lot more\n> flags.\n>\n> I only marked the first patch as a \"Fix\" since it is the only one\n> fixing observed problems. Other patches could be considered fixes too\n> if folks want.\n>\n> I tested the first patch in the series backported to kernel 6.6 on the\n> Pixel phone that was experiencing the race. I added extra printouts to\n> make sure that the problem was hitting / addressed. The rest of the\n> patches are tested with allmodconfig with arm32, arm64, ppc, and\n> x86. I boot tested on an arm64 Chromebook running mainline.\n>\n> Changes in v4:\n> - Use accessor functions for flags\n>\n> Changes in v3:\n> - Use a new \"flags\" bitfield\n> - Add missing \\n in probe error message\n>\n> Changes in v2:\n> - Instead of adjusting the ordering, use \"ready_to_probe\" flag\n>\n> Douglas Anderson (9):\n> driver core: Don't let a device probe until it's ready\n> driver core: Replace dev->can_match with dev_can_match()\n> driver core: Replace dev->dma_iommu with dev_dma_iommu()\n> driver core: Replace dev->dma_skip_sync with dev_dma_skip_sync()\n> driver core: Replace dev->dma_ops_bypass with dev_dma_ops_bypass()\n> driver core: Replace dev->state_synced with dev_state_synced()\n> driver core: Replace dev->dma_coherent with dev_dma_coherent()\n> driver core: Replace dev->of_node_reused with dev_of_node_reused()\n> driver core: Replace dev->offline + ->offline_disabled with accessors\n>\n> arch/arc/mm/dma.c | 4 +-\n> arch/arm/mach-highbank/highbank.c | 2 +-\n> arch/arm/mach-mvebu/coherency.c | 2 +-\n> arch/arm/mm/dma-mapping-nommu.c | 4 +-\n> arch/arm/mm/dma-mapping.c | 28 ++--\n> arch/arm64/kernel/cpufeature.c | 2 +-\n> arch/arm64/mm/dma-mapping.c | 2 +-\n> arch/mips/mm/dma-noncoherent.c | 2 +-\n> arch/powerpc/kernel/dma-iommu.c | 8 +-\n> .../platforms/pseries/hotplug-memory.c | 4 +-\n> arch/riscv/mm/dma-noncoherent.c | 2 +-\n> drivers/acpi/scan.c | 2 +-\n> drivers/base/core.c | 53 +++++---\n> drivers/base/cpu.c | 4 +-\n> drivers/base/dd.c | 28 ++--\n> drivers/base/memory.c | 2 +-\n> drivers/base/pinctrl.c | 2 +-\n> drivers/base/platform.c | 2 +-\n> drivers/dma/ti/k3-udma-glue.c | 6 +-\n> drivers/dma/ti/k3-udma.c | 6 +-\n> drivers/iommu/dma-iommu.c | 9 +-\n> drivers/iommu/iommu.c | 5 +-\n> drivers/net/pcs/pcs-xpcs-plat.c | 2 +-\n> drivers/of/device.c | 6 +-\n> drivers/pci/of.c | 2 +-\n> drivers/pci/pwrctrl/core.c | 2 +-\n> drivers/regulator/bq257xx-regulator.c | 2 +-\n> drivers/regulator/rk808-regulator.c | 2 +-\n> drivers/tty/serial/serial_base_bus.c | 2 +-\n> drivers/usb/gadget/udc/aspeed-vhub/dev.c | 2 +-\n> include/linux/device.h | 120 ++++++++++++------\n> include/linux/dma-map-ops.h | 6 +-\n> include/linux/dma-mapping.h | 2 +-\n> include/linux/iommu-dma.h | 3 +-\n> kernel/cpu.c | 4 +-\n> kernel/dma/mapping.c | 12 +-\n> mm/hmm.c | 2 +-\n> 37 files changed, 206 insertions(+), 142 deletions(-)\n>\n> --\n\nFor the whole set\n\nReviewed-by: Rafael J. 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Wysocki\" ","Date":"Sat, 4 Apr 2026 19:11:59 +0200","X-Gmail-Original-Message-ID":"\n ","X-Gm-Features":"AQROBzCS1sK1yep87rT-2xolltVfQ4j4qlt-9lHai0wQJnu4V3tzUHOX8_7jVCo","Message-ID":"\n ","Subject":"Re: [PATCH v4 0/9] driver core: Fix some race conditions","To":"Douglas Anderson ","Cc":"Greg Kroah-Hartman ,\n \"Rafael J . Wysocki\" ,\n\tDanilo Krummrich , Alan Stern ,\n\tSaravana Kannan , Christoph Hellwig ,\n Eric Dumazet ,\n\tJohan Hovold , Leon Romanovsky ,\n\tAlexander Lobakin ,\n Alexey Kardashevskiy ,\n\tRobin Murphy ,\n Andrew Morton , Frank.Li@kernel.org,\n\tJason Gunthorpe , alex@ghiti.fr,\n alexander.stein@ew.tq-group.com,\n\tandre.przywara@arm.com, andrew@codeconstruct.com.au, andrew@lunn.ch,\n\tandriy.shevchenko@linux.intel.com, aou@eecs.berkeley.edu, ardb@kernel.org,\n\tbhelgaas@google.com, brgl@kernel.org, broonie@kernel.org,\n\tcatalin.marinas@arm.com, chleroy@kernel.org, davem@davemloft.net,\n\tdavid@kernel.org, devicetree@vger.kernel.org, dmaengine@vger.kernel.org,\n\tdriver-core@lists.linux.dev, gbatra@linux.ibm.com,\n\tgregory.clement@bootlin.com, hkallweit1@gmail.com, iommu@lists.linux.dev,\n\tjirislaby@kernel.org, joel@jms.id.au, joro@8bytes.org, kees@kernel.org,\n\tkevin.brodsky@arm.com, kuba@kernel.org, lenb@kernel.org, lgirdwood@gmail.com,\n\tlinux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,\n\tlinux-aspeed@lists.ozlabs.org, linux-cxl@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org,\n\tlinux-pci@vger.kernel.org, linux-riscv@lists.infradead.org,\n\tlinux-serial@vger.kernel.org, linux-snps-arc@lists.infradead.org,\n\tlinux-usb@vger.kernel.org, linux@armlinux.org.uk,\n\tlinuxppc-dev@lists.ozlabs.org, m.szyprowski@samsung.com, maddy@linux.ibm.com,\n\tmani@kernel.org, maz@kernel.org, miko.lenczewski@arm.com, mpe@ellerman.id.au,\n\tnetdev@vger.kernel.org, npiggin@gmail.com, osalvador@suse.de,\n\toupton@kernel.org, pabeni@redhat.com, palmer@dabbelt.com,\n\tpeter.ujfalusi@gmail.com, peterz@infradead.org, pjw@kernel.org,\n\trobh@kernel.org, sebastian.hesselbarth@gmail.com, tglx@kernel.org,\n\ttsbogend@alpha.franken.de, vgupta@kernel.org, vkoul@kernel.org,\n\twill@kernel.org, willy@infradead.org, yangyicong@hisilicon.com,\n\tyeoreum.yun@arm.com","Content-Type":"text/plain; charset=\"UTF-8\"","Content-Transfer-Encoding":"quoted-printable","X-Spam-Status":"No, score=-0.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}}]