Em Sat, Mar 23, 2019 at 04:04:22PM +0100, Jiri Olsa escreveu: > On Fri, Mar 15, 2019 at 03:52:25PM +0100, Jiri Olsa wrote: > > On Fri, Mar 15, 2019 at 11:35:04AM -0300, Arnaldo Carvalho de Melo wrote: > > > The perf_evsel__open() code is already complex with that fallback > > > mechanism, this is just one more way of fallbacking when asking the > > > kernel for something that may fail.
> > > In fact what happens if the precise_ip that is being asked _is_ > > > supported but sys_perf_event_open() fails because some other > > > perf_event_attr attribute that is set is not supported? > > it's outside the scope of standard feature fallback code, > > so we will try it for any possible fallback variant, so: > > we will try all possible precise_ip (3,2,1,0) and they will > > all fail because of the unsupported attribute - so we will > > restore the precise_ip back and continue in standard fallback > > code that will eventualy switch that attribute off > > > I see, it gets it back restored to what the user asked so that the > > > standard fallback is tried, ok, I'll apply with just the rename for this > > > function, > ping, there's rebased version in my perf/fixes branch Thanks, applied. - Arnaldo
