On Fri, Mar 19, 2021 at 7:06 PM Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > On Fri, Mar 19, 2021 at 06:00:38PM +0100, Rafael J. Wysocki wrote: > > On Fri, Mar 12, 2021 at 5:02 PM Andy Shevchenko > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > > > > Current mechanism of incrementing and decrementing plain integer > > > to get a next free instance_no when creating an ACPI device is fragile. > > > > > > In case of hot plug event or namespace removal of the device instances > > > with the low numbers the plain integer counter can't cover the gaps > > > and become desynchronized with real state of affairs. If during next > > > hot plug event or namespace injection the new instances of > > > the devices need to be instantiated, the counter may mistakenly point > > > to the existing instance_no and kernel will complain: > > > "sysfs: cannot create duplicate filename '/bus/acpi/devices/XXXX1234:02'" > > > > This is a slightly convoluted way of stating that there is a bug in > > acpi_device_del(). > > Any suggestion how to massage the above? Why don't you simply say something like "The decrementation of acpi_device_bus_id->instance_no in acpi_device_del() is incorrect, because it may cause a duplicate instance number to be allocated next time a device with the same acpi_device_bus_id is added."
