On Wed, Jan 28, 2015 at 01:24:12AM +0100, Frederic Weisbecker wrote: > PREEMPT_ACTIVE implies non-preemptible context and thus atomic context > despite what in_atomic*() APIs reports about it. These functions > shouldn't ignore this value like they are currently doing. > > It appears that these APIs were ignoring PREEMPT_ACTIVE in order to > ease the check in schedule_debug(). Meanwhile it is sufficient to rely > on PREEMPT_ACTIVE in order to disable preemption in __schedule(). > > So lets fix the in_atomic*() APIs and simplify the preempt count ops > on __schedule() callers.
So what I think the history is here is that PREEMPT_ACTIVE is/was seen as a flag, protecting recursion, not so much a preempt-disable. By doing this, you loose that separation. Note that (at least on x86) we have another flag in the preempt count. And I don't think the generated code really changes, the only difference is the value added/subtracted and that's an encoded immediate I think. -- 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/
