Messages in this thread | | | Date | Tue, 3 Jan 2023 15:24:16 +0000 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH v2] nvmem: fix registration vs use race |
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On Wed, Jan 04, 2023 at 12:20:15AM +0900, Hector Martin wrote: > On 03/01/2023 23.42, Russell King (Oracle) wrote: > > The i.MX6 CPU frequency driver sometimes fails to register at boot time > > due to nvmem_cell_read_u32() sporadically returning -ENOENT. > > > > This happens because there is a window where __nvmem_device_get() in > > of_nvmem_cell_get() is able to return the nvmem device, but as cells > > have been setup, nvmem_find_cell_entry_by_node() returns NULL. > > > > The occurs because the nvmem core registration code violates one of the > > fundamental principles of kernel programming: do not publish data > > structures before their setup is complete. > > > > Fix this by making nvmem core code conform with this principle. > > > > Fixes: eace75cfdcf7 ("nvmem: Add a simple NVMEM framework for nvmem providers") > > Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> > > --- > > v2: add fixes tag > > > > drivers/nvmem/core.c | 18 ++++++++---------- > > 1 file changed, 8 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c > > index 321d7d63e068..6b89fb6fa582 100644 > > --- a/drivers/nvmem/core.c > > +++ b/drivers/nvmem/core.c > > @@ -835,22 +835,16 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > > nvmem->dev.groups = nvmem_dev_groups; > > #endif > > > > - dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); > > - > > - rval = device_register(&nvmem->dev); > > - if (rval) > > - goto err_put_device; > > - > > if (nvmem->nkeepout) { > > rval = nvmem_validate_keepouts(nvmem); > > if (rval) > > - goto err_device_del; > > + goto err_put_device; > > You can't call put_device() on a device that hasn't gone through > device_initialize() yet.
Right, which is what I just realised while writing the previous reply. We need to use device_initialize() and device_add(), so we can call put_device() on it.
Error paths are difficult to properly test. :(
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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