On Wed, 25 Apr 2018 17:40:56 -0400 (EDT) Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote:
> One problem with your approach is that you can have multiple callers > for the same tracepoint name, where some could be non-preemptible and > others blocking. Also, there is then no clear way for the callback > registration API to enforce whether the callback expects the tracepoint > to be blocking or non-preemptible. This can introduce hard to diagnose > issues in a kernel without debug options enabled. I agree that it should not be tied to an implementation name. But "blocking" is confusing. I would say "can_sleep" or some such name that states that the trace point caller is indeed something that can sleep. > > Regarding the name, I'm OK with having something along the lines of > trace_*event*_blocking or such. Please don't use "srcu" or other naming > that is explicitly tied to the underlying mechanism used internally > however: what we want to convey is that this specific tracepoint probe > can be preempted and block. The underlying implementation could move to > a different RCU flavor brand in the future, and it should not impact > users of the tracepoint APIs. > > In order to ensure that probes that may block only register themselves > to tracepoints that allow blocking, we should introduce new tracepoint > declaration/definition *and* registration APIs also contain the > "BLOCKING/blocking" keywords (or such), so we can ensure that a > tracepoint probe being registered to a "blocking" tracepoint is indeed > allowed to block. I'd really don't want to add more declaration/definitions, as we already have too many as is, and with different meanings and the number is of incarnations is n! in growth. I'd say we just stick with a trace_<event>_can_sleep() call, and make sure that if that is used that no trace_<event>() call is also used, and enforce this with linker or compiler tricks. -- Steve
