On Tue, Sep 29, 2015 at 07:55:49AM -0400, Linus Torvalds wrote: > On Tue, Sep 29, 2015 at 6:56 AM, Peter Zijlstra <pet...@infradead.org> wrote: > > > > + * Initial preempt_count value; reflects the preempt_count schedule > > invariant > > + * which states that during schedule preempt_count() == 2. > > Is this actually *true*? > > preempt_count() is two only if preemption is enabled. But spinlocks do > not actually update the preemption count if there is no preemption, so > these kinds of checks and comments that aren't even inside #ifdef > CONFIG_PREEMPT seem to be actively misleading. > > I do believe that the preempt count is stable - but the actual value > would seem to depend on config options.
Right, 2*PREEMPT_DISABLE_OFFSET is the 'right' number. That ends up being 0 for !PREEMPT_COUNT configs. I'll update the Changelog to be more accurate on this. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
