[PATCH -v2 01/18] sched/fair: Clean up calc_cfs_shares()

[Peter Zijlstra]

For consistencies sake, we should have only a single reading of
tg->shares.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 kernel/sched/fair.c |   31 ++++++++++++-------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2633,9 +2633,12 @@ account_entity_dequeue(struct cfs_rq *cf
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 # ifdef CONFIG_SMP
-static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
+static long calc_cfs_shares(struct cfs_rq *cfs_rq)
 {
-       long tg_weight, load, shares;
+       long tg_weight, tg_shares, load, shares;
+       struct task_group *tg = cfs_rq->tg;
+
+       tg_shares = READ_ONCE(tg->shares);
 
        /*
         * This really should be: cfs_rq->avg.load_avg, but instead we use
@@ -2650,7 +2653,7 @@ static long calc_cfs_shares(struct cfs_r
        tg_weight -= cfs_rq->tg_load_avg_contrib;
        tg_weight += load;
 
-       shares = (tg->shares * load);
+       shares = (tg_shares * load);
        if (tg_weight)
                shares /= tg_weight;
 
@@ -2666,17 +2669,7 @@ static long calc_cfs_shares(struct cfs_r
         * case no task is runnable on a CPU MIN_SHARES=2 should be returned
         * instead of 0.
         */
-       if (shares < MIN_SHARES)
-               shares = MIN_SHARES;
-       if (shares > tg->shares)
-               shares = tg->shares;
-
-       return shares;
-}
-# else /* CONFIG_SMP */
-static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group 
*tg)
-{
-       return tg->shares;
+       return clamp_t(long, shares, MIN_SHARES, tg_shares);
 }
 # endif /* CONFIG_SMP */
 
@@ -2701,7 +2694,6 @@ static inline int throttled_hierarchy(st
 static void update_cfs_shares(struct sched_entity *se)
 {
        struct cfs_rq *cfs_rq = group_cfs_rq(se);
-       struct task_group *tg;
        long shares;
 
        if (!cfs_rq)
@@ -2710,13 +2702,14 @@ static void update_cfs_shares(struct sch
        if (throttled_hierarchy(cfs_rq))
                return;
 
-       tg = cfs_rq->tg;
-
 #ifndef CONFIG_SMP
-       if (likely(se->load.weight == tg->shares))
+       shares = READ_ONCE(cfs_rq->tg->shares);
+
+       if (likely(se->load.weight == shares))
                return;
+#else
+       shares = calc_cfs_shares(cfs_rq);
 #endif
-       shares = calc_cfs_shares(cfs_rq, tg);
 
        reweight_entity(cfs_rq_of(se), se, shares);
 }