I hate having to justify why breaking the ABI is unacceptable. On Mon, 22 Jul 2013, Andi Kleen wrote: > On Tue, Jul 23, 2013 at 01:40:40AM -0400, Vince Weaver wrote: > > On Mon, 22 Jul 2013, Andi Kleen wrote: > > > > > From: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > > > > > Add a precise qualifier, like cpu/event=0x3c,precise=1/ > > > > So you're adding this to "events/" but not to "format/"? > > Fair point, but note that precise_ip is a bitfield. Since there is no > way to express that currently the parser would need to special case it anyways. It breaks the ABI. The events/* sysfs files are documented as only holding values for the bitfields described in format/*. The perf_event ABI is there for all tools, not to just be a thin shim for the perf tool. Even if the maintainers for whatever are going to just ignore the ABI, then fine, but then I'd like to see a patch also updating the sysfs ABI documentation and a patch to the perf_event_open.2 manpage would be nice as well. > > This will break various existing programs. > > Like what? Why does it matter? It breaks multiple programs I work on. A major one is the trinity fuzzer, which parses perf_event sysfs to construct valid events. The code won't segfault because I wrote the parser to be robust, but it will spit a warning when invalid junk is put in the sysfs events files, and I'll get e-mails about it spamming trinity runs with warning messages within hours of such a commit hitting linus-git. I'm a bit grumpy about this because I just finished fixing the fallout from your last time breaking the ABI a few weeks ago when your broken code started dumping non-hex fields into the sysfs event strings. I've learned now that I have to go over your patches with a fine-tooth code because you have no regard for the ABI. Vince -- To unsubscribe from this list: send the line "unsubscribe trinity" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
