On Wed, Sep 05, 2012 at 06:40:26PM +0900, Takuya Yoshikawa wrote: > On Wed, 5 Sep 2012 12:26:49 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > It's not guaranteed if another thread can modify the bitmap. > > Is this the case here? If yes we need at least ACCESS_ONCE. > > In this patch, using the wrapper function to read out a register > value forces compilers not to do bad things.
It's not robust. Compiler is free to optimize it out, and it frequently does that. > But I agree that it is not a good API. > > I would like to use fls() rather than ACCESS_ONCE if it's > really needed. Sure, makes sense. > > > Anyway, I'm now thinking that we do not care about such > > > things here, and can just follow your advice, yes? > > > > Unless you see an issue with it ... > > Although I read the code, I'm not sure. > > But this code is apparently not so critical for performance > that we can simply use fls(). Yes. I guess if it becomes critical we'll need to add a cache anyway. > If I can remove likely() and use proper macros, that's enough > for me. Me too. > Thanks, > Takuya -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
