On Tue, Dec 13, 2016 at 11:10:50AM +0200, Jani Nikula wrote: > On Tue, 13 Dec 2016, Nicholas Mc Guire <hofrat@xxxxxxxxx> wrote: > > useleep_range() with a delta of 0 makes no sense and only prevents the > > timer subsystem from optimizing interrupts. As any user of usleep_range() > > is in non-atomic context the timer jitter is in the range of 10s of > > microseconds anyway. > > > > This adds a note making it clear that a range of 0 is a bad idea. > > So I don't really have anything to do with the timer subsystem, I'm just > their "consumer", so take this with a grain of salt. > > Documentation is good, but I don't think this will be enough. > > I think the only thing that will work is to detect and complain about > things like this automatically. Some ideas: > > * WARN_ON(min == max) or WARN_ON_ONCE(min == max) in usleep_range() > might be drastic, but it would get the job done eventually. > > * If you want to avoid the runtime overhead (and complaints about the > backtraces), you could wrap usleep_range() in a macro that does > BUILD_BUG_ON(min == max) if the parameters are build time constants > (they usually are). But you'd have to fix all the problem cases first. > > * You could try (to persuade Julia or Dan) to come up with a > cocci/smatch check for usleep_range() calls where min == max, so we > could get bug reports for this. This probably works on expressions, so > this would catch also cases where the parameters aren't built time > constants. > I fully agree - without automation it is almost usless the coccinelle spatch is a seperate patch and it is tested butnot yet submitted. the spatch for this iss actually trivial @nulldelta@ constant C; position p; @@ * usleep_range@p(C,C) thx! hofrat -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
