On Mon, Jul 23, 2018 at 11:27:10AM -0700, Guenter Roeck wrote: > On Mon, Jul 23, 2018 at 10:23:05AM -0700, Dmitry Torokhov wrote: > > On Mon, Jul 23, 2018 at 10:13:36AM -0700, Guenter Roeck wrote: > > > On Mon, Jul 23, 2018 at 07:48:57PM +0300, Anton Vasilyev wrote: > > > > static struct ro_vpd and rw_vpd are initialized by vpd_sections_init() > > > > in vpd_probe() based on header's ro and rw sizes. > > > > In vpd_remove() vpd_section_destroy() performs deinitialization based > > > > on enabled flag, which is set to true by vpd_sections_init(). > > > > This leads to call of vpd_section_destroy() on already destroyed section > > > > for probe-release-probe-release sequence if first probe performs > > > > ro_vpd initialization and second probe does not initialize it. > > > > > > > > > > I am not sure if the situation described can be seen in the first place. > > > The second probe would only not perform ro_vpd initialization if it fails > > > prior to that, ie if it fails to allocate memory or if there is a > > > consistency problem. In that case the remove function would not be called. > > > > > > However, there is a problem in the code: A partially failed probe will > > > leave the system in inconsistent state. Example: ro section initializes, > > > rw section fails to initialize. The probe will fail, but the ro section > > > will not be destroyed, its sysfs attributes still exist, and its memory > > > is still mapped. It would make more sense to fix _that_ problem. > > > Essentially, vpd_sections_init() should clean up after itself after it > > > fails to initialize a section. > > > > > > Note that I am not convinced that the "enabled" flag is needed in the > > > first > > > place. It is only relevant if vpd_section_destroy() is called, which only > > > happens from the remove function. The remove function is only called if > > > the > > > probe function succeeded. In that case it is always set for both sections. > > > > The problem will happen if coreboot memory changes between 2 probes so > > that header.ro_size is not 0 on the first pass and is 0 on the second > > pass. Not quite likely to ever happen in real life, but resetting a flag > > is pretty cheap to not do it. > > > > If that can happen between probes, meaning it is not guaranteed to be > constant during the lifetime of the system, doesn't that mean it can > happen anytime ?
I think we can assume that the data is stable while coreboot device is registered, but I can imagine one can theoretically have a debug coreboot data provider that can supply different coreboot parameters across load/unload. I.e. we have coreboot_table-acpi.c and coreboot_table-of.c, we might create coreboot_table-test.c to feed arbitrary data to the subsystem. Thanks. -- Dmitry
