On 09/24, Steven Rostedt wrote: > > On Tue, 24 Sep 2013 18:03:59 +0200 > Oleg Nesterov <[email protected]> wrote: > > > On 09/24, Peter Zijlstra wrote: > > > > > > +static inline void get_online_cpus(void) > > > +{ > > > + might_sleep(); > > > + > > > + if (current->cpuhp_ref++) { > > > + barrier(); > > > + return; > > > > I don't undestand this barrier()... we are going to return if we already > > hold the lock, do we really need it? > > I'm confused too. Unless gcc moves this after the release, but the > release uses preempt_disable() which is its own barrier. > > If anything, it requires a comment.
And I am still confused even after emails from Paul and Peter... If gcc can actually do something wrong, then I suspect this barrier() should be unconditional. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
