On Mon, Aug 22, 2011 at 11:50 AM, Sriraman Tallam <tmsri...@google.com> wrote: > On Mon, Aug 22, 2011 at 9:02 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Mon, Aug 22, 2011 at 8:56 AM, Michael Matz <m...@suse.de> wrote: >>> Hi, >>> >>> On Mon, 22 Aug 2011, H.J. Lu wrote: >>> >>>> >> Oh, I thought it was data initialized by the constructor ... >>>> > >>>> > Sriramans patch right now has a function __cpu_indicator_init which is >>>> > called from (adhoc constructed) ctors and that initializes variables >>>> > __cpu_model and __cpu_features ;-) There's no __cpu_indicator symbol :) >>>> > >>>> > I think the whole initializer function and the associated data blobs have >>>> > to sit in static libgcc and be hidden. By that all shared modules >>>> > will have their own copies of the model and features (and the initializer >>>> > function) so there won't be issues with copy relocs, or cross shared lib >>>> > calls while relocating the modules. Dynamically they will contain the >>>> > same data always, but it's not many bytes, and only modules making use of >>>> > this facility will pay it. >>>> > >>>> > The initializer function has to be callable from pre-.init contexts, e.g. >>>> > ifunc dispatchers. And to make life easier there should be one ctor >>>> > function calling this initializer function too, so that normal code can >>>> > rely on it being already called saving one check. >>>> > >>>> >>>> It sounds more complicated than necessary. Why not just do it >>>> on demand like glibc does? >>> >>> Ehm, the only difference would be to not have a ctor in libgcc that looks >>> like so: >>> >>> void __attribute__((constructor)) bla(void) >>> { >>> __cpu_indicator_init (); >>> } >>> >>> I don't see any complication.? >>> >> >> Order of constructors. A constructor may call functions >> which use __cpu_indicator. > > I have a suggestion that is a hybrid of the proposed solutions here: > > 1) Make a constructor in every module that calls > "__cpu_indicator_init" and make it to be the first constructor to run. > Will this solve the ordering problem? > 2) Change __cpu_indicator_init to run only once by using a variable to > check if it has been run before. > > So, each module's constructor will call __cpu_indicator_init but the > CPUID insns are only done once. I also avoid the extra overhead of > having to check if "__cpu_indicator_init" is called from within the > binary. Will this work? >
Please make it simple like if __cpu_indicator is not initialized then call __cpu_indicator_init fi use __cpu_indicator -- H.J.