Messages in this thread | | | Date | Thu, 9 Mar 2023 12:05:07 +0100 | From | Greg KH <> | Subject | Re: [PATCH v3] uio:uio_pci_generic:Don't clear master bit when the process does not exit |
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On Sat, Mar 04, 2023 at 03:43:16PM +0800, Su Weifeng wrote: > From: Weifeng Su <suweifeng1@huawei.com> > > The /dev/uioX device has concurrent operations in a few scenarios.
And you just broke that :(
> For example, when a process is operating the uio0 device, someone executes > like "cat /dev/uio0" command. In this case, the bus master bit is cleared > unconditionally.
It is cleared when the close happens, not when "cat" runs.
So prevent userspace from doing that with permissions, why must the kernel enforce this policy you are making?
> As a result, the running program cannot work commands > or I/Os, which is usually unaware of. This happens after > 865a11f("uio/uio_pci_generic: Disable bus-mastering on release");
Please always reference commits in the documented way.
> The restriction on the process that uses the PCI device is added. The new > process can be used only after the process that uses the PCI device exits. > Otherwise, the system returns a message indicating that the device is busy.
Again, you are changing the functionality of the kernel, are you sure you did not just now break something else?
thanks,
greg k-h
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