On Wed, Jul 16, 2014 at 11:53:23AM -0700, [email protected] wrote: > Morten Rasmussen <[email protected]> writes: > > > On Wed, Jul 16, 2014 at 02:50:47AM +0100, Yuyang Du wrote: > > > > [...] > > > >> +/* > >> + * Update load_avg of the cfs_rq along with its own se. They should get > >> + * synchronized: group se's load_avg is used for task_h_load calc, and > >> + * group cfs_rq's load_avg is used for task_h_load (and update_cfs_share > >> + * calc). > >> + */ > >> +static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) > >> { > >> - long old_contrib = se->avg.load_avg_contrib; > >> + int decayed; > >> > >> - if (entity_is_task(se)) { > >> - __update_task_entity_contrib(se); > >> - } else { > >> - __update_tg_runnable_avg(&se->avg, group_cfs_rq(se)); > >> - __update_group_entity_contrib(se); > >> + if (atomic_long_read(&cfs_rq->removed_load_avg)) { > >> + long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0); > >> + cfs_rq->avg.load_avg = > >> subtract_until_zero(cfs_rq->avg.load_avg, r); > >> + r *= LOAD_AVG_MAX; > >> + cfs_rq->avg.load_sum = > >> subtract_until_zero(cfs_rq->avg.load_sum, r); > >> } > >> > >> - return se->avg.load_avg_contrib - old_contrib; > >> -} > >> + decayed = __update_load_avg(now, &cfs_rq->avg, > >> cfs_rq->load.weight); > >> +#ifndef CONFIG_64BIT > >> + if (cfs_rq->avg.last_update_time != > >> cfs_rq->load_last_update_time_copy) > >> + sa_q->last_update_time_copy = sa_q->last_update_time; > > > > to make it build. But I'm not convinced that this synchronization is > > right. > > > > First let me say that I'm not an expert on synchronization. It seems to > > me that there is nothing preventing reordering of the writes in > > __update_load_avg() which sets cfs_rq->avg.last_update_time and the > > update of cfs_rq->avg.load_last_update_time_copy. > > You're correct, this needs to be if(...) { smp_wmb(); copy = time; }, > the same as update_min_vruntime.
Ok, I will get the barrier back. Thanks, Morten and Ben. Yuyang -- 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/
