On 10/14/2013 02:03 PM, Peter Zijlstra wrote: > On Mon, Oct 14, 2013 at 12:43:36PM +0200, Juri Lelli wrote: >> +static inline void dl_set_overload(struct rq *rq) >> +{ >> + if (!rq->online) >> + return; >> + >> + cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask); >> + /* >> + * Must be visible before the overload count is >> + * set (as in sched_rt.c). >> + */ >> + wmb(); >> + atomic_inc(&rq->rd->dlo_count); >> +} > > Please, make that smp_wmb() and modify the comment to point to the > matching barrier ; I couldn't find one! Which suggests something is > amiss. > > Ideally we'd have something like smp_wmb__after_set_bit() but alas. >
The only user of this function is pull_dl_task (that tries to pull only if at least one runqueue of the root_domain is overloaded). Surely makes sense to ensure that changes in the dlo_mask have to be visible before we check if we should look at that mask. Am I right if I say that the matching barrier is constituted by the spin_lock on this_rq acquired by schedule() before calling pre_schedule()? Same thing in rt_set_overload(), do we need to modify the comment also there? Thanks, - Juri -- 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/