Hi Dietmar! On 15-Aug 12:59, Dietmar Eggemann wrote: > On 08/15/2018 12:54 PM, Patrick Bellasi wrote: > >On 15-Aug 11:37, Dietmar Eggemann wrote: > >>On 08/14/2018 06:49 PM, Patrick Bellasi wrote:
[...] > >>If this is only for testing/debugging, I would suggest a simple one line > >>BUG_ON() > > > >These are (eventually) considered as recoverable errors... thus, > >AFAIK, using BUG_ON is overkilling and discouraged: > > > > https://elixir.bootlin.com/linux/latest/source/include/asm-generic/bug.h#L42 > > Not sure about that. If this refcounting is out of sync, that's indicating a > serious issue here for me which should be fixed. Well, refconting seems quite ok to me, we always inc/dec under RQ locking and it's a per-CPU variable. The warning is there to report issues on further testing as well as to be safe with respect to possible future modifications of the code. > >>You find CONFIG_SCHED_DEBUG=y in production kernels as well. > > > >AFAIK, that setting is discouraged for production kernels... > >Moreover, it's still better to WARN sometimes on a production kernel > >the crash the device, isnt't it? > > IMHO, if this is something which should not happen at all, a BUG_ON() is the > right thing to do here. I don't agree on that. I agree it should not happen but since it's a recoverable error it think we should not panic. There are really few BUG_ON() in core.c and they are all for much more serious issues than a (eventually) broken refcount. IMHO instead an (unlikely) inconsistent refcont for an "optional optimization" on "frequency selection" is not such a critical failure worth a device crash. > And you get the call stack to investigate why it hit. We can always add a stack dump if we notice the warning. But, since we do not agree on that point, I would say we should better wait for what the maintainers prefers. Best, Patrick -- #include <best/regards.h> Patrick Bellasi
