On Thu, Apr 14, 2011 at 09:18:57PM -0400, Natarajan Gurumoorthy wrote: > On Thu, Apr 14, 2011 at 3:49 PM, Guenter Roeck > <guenter.roeck@xxxxxxxxxxxx> wrote: > > This is way too complicated. Just return an error if > > request_muxed_region fails, like all other callers of > > request_muxed_region do. > > > Guenter, > This maybe a little complicated but it is a solution that will > correctly deal with the following scenario: > Hardware: it8712f > cpu: Multicore > kernel: smp > Modules being loaded during initialization: it8712f_wtd and w83697hf > > The problem is one of the cores is halfway through initializing > it8712f_wdt and another core is just starting to run the > "w83697hf_check_wdt" which is going to call "request_region" to > reserve 0x2e 0x2f region. Just after that call on the other core > it8712f_wdt_init calls it8712f_wdt_disable which calls superio_enter > which will call "request_muxed_region" for the exact same region. This > is guaranteed to fail because as of now w83697hf is one of the many > non compliant drivers who are calling "request_region". The w83697hf > will do the probe and conclude there is no w83697hf chip in the system > and abort rest of the driver initialization. Meanwhile the it8712f_wtd > driver initialization will fail. This will be one of those > intermittent failures that make most kernel device driver writers > prematurely bald :-). > > The way I have reworked the driver will survive the above scenario. > Unless I am missing something, the problem is that there is another driver calling request_region() instead of request_muxed_region(). w83697hf_check_wdt() (and other drivers doing the same) should call request_muxed_region(). Otherwise, the same problem could happen with the caller(s) of request_region() - those calls could fail as well. Plus, other callers of request_muxed_reason() not implementing your retry code could end up with the same problem, ie with spurious failures. I think we will have to find a solution which does not require retries when calling request_muxed_region(). On the other side, others know this code much better than I do, so maybe someone has a better solution. Thanks, Guenter _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
