sched/fair: Switch to rcu_dereference_all()

With the {rcu,sched,bh} RCU flavours being unified, it doesn't really
make sense to check for just the rcu one. Switch to the _all family of
verification which includes all 3 of the listed flavours.

Notably, this will enable us to remove some superfluous
rcu_read_lock() regions when we know they are inside preempt/IRQ
disabled regions.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 74a0550b4552a4d19e3c5ae54310d5394c82fe7d..44a359d6a299f1837cb3166d9fbe2d019efd4beb 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1513,7 +1513,7 @@ static unsigned int task_scan_start(struct task_struct *p)
 
        /* Scale the maximum scan period with the amount of shared memory. */
        rcu_read_lock();
-       ng = rcu_dereference(p->numa_group);
+       ng = rcu_dereference_all(p->numa_group);
        if (ng) {
                unsigned long shared = group_faults_shared(ng);
                unsigned long private = group_faults_priv(ng);
@@ -1580,7 +1580,7 @@ pid_t task_numa_group_id(struct task_struct *p)
        pid_t gid = 0;
 
        rcu_read_lock();
-       ng = rcu_dereference(p->numa_group);
+       ng = rcu_dereference_all(p->numa_group);
        if (ng)
                gid = ng->gid;
        rcu_read_unlock();
@@ -2239,7 +2239,7 @@ static bool task_numa_compare(struct task_numa_env *env,
                return false;
 
        rcu_read_lock();
-       cur = rcu_dereference(dst_rq->curr);
+       cur = rcu_dereference_all(dst_rq->curr);
        if (cur && ((cur->flags & (PF_EXITING | PF_KTHREAD)) ||
                    !cur->mm))
                cur = NULL;
@@ -2284,7 +2284,7 @@ static bool task_numa_compare(struct task_numa_env *env,
         * If dst and source tasks are in the same NUMA group, or not
         * in any group then look only at task weights.
         */
-       cur_ng = rcu_dereference(cur->numa_group);
+       cur_ng = rcu_dereference_all(cur->numa_group);
        if (cur_ng == p_ng) {
                /*
                 * Do not swap within a group or between tasks that have
@@ -2499,7 +2499,7 @@ static int task_numa_migrate(struct task_struct *p)
         * to satisfy here.
         */
        rcu_read_lock();
-       sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
+       sd = rcu_dereference_all(per_cpu(sd_numa, env.src_cpu));
        if (sd) {
                env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
                env.imb_numa_nr = sd->imb_numa_nr;
@@ -3022,7 +3022,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
        if (!cpupid_match_pid(tsk, cpupid))
                goto no_join;
 
-       grp = rcu_dereference(tsk->numa_group);
+       grp = rcu_dereference_all(tsk->numa_group);
        if (!grp)
                goto no_join;
 
@@ -4435,7 +4435,7 @@ static inline void migrate_se_pelt_lag(struct sched_entity *se)
        rq = rq_of(cfs_rq);
 
        rcu_read_lock();
-       is_idle = is_idle_task(rcu_dereference(rq->curr));
+       is_idle = is_idle_task(rcu_dereference_all(rq->curr));
        rcu_read_unlock();
 
        /*
@@ -7462,7 +7462,7 @@ static inline void set_idle_cores(int cpu, int val)
 {
        struct sched_domain_shared *sds;
 
-       sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+       sds = rcu_dereference_all(per_cpu(sd_llc_shared, cpu));
        if (sds)
                WRITE_ONCE(sds->has_idle_cores, val);
 }
@@ -7471,7 +7471,7 @@ static inline bool test_idle_cores(int cpu)
 {
        struct sched_domain_shared *sds;
 
-       sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+       sds = rcu_dereference_all(per_cpu(sd_llc_shared, cpu));
        if (sds)
                return READ_ONCE(sds->has_idle_cores);
 
@@ -7600,7 +7600,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool
        cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
        if (sched_feat(SIS_UTIL)) {
-               sd_share = rcu_dereference(per_cpu(sd_llc_shared, target));
+               sd_share = rcu_dereference_all(per_cpu(sd_llc_shared, target));
                if (sd_share) {
                        /* because !--nr is the condition to stop scan */
                        nr = READ_ONCE(sd_share->nr_idle_scan) + 1;
@@ -7806,7 +7806,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
         * sd_asym_cpucapacity rather than sd_llc.
         */
        if (sched_asym_cpucap_active()) {
-               sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
+               sd = rcu_dereference_all(per_cpu(sd_asym_cpucapacity, target));
                /*
                 * On an asymmetric CPU capacity system where an exclusive
                 * cpuset defines a symmetric island (i.e. one unique
@@ -7821,7 +7821,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
                }
        }
 
-       sd = rcu_dereference(per_cpu(sd_llc, target));
+       sd = rcu_dereference_all(per_cpu(sd_llc, target));
        if (!sd)
                return target;
 
@@ -8290,7 +8290,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
        struct energy_env eenv;
 
        rcu_read_lock();
-       pd = rcu_dereference(rd->pd);
+       pd = rcu_dereference_all(rd->pd);
        if (!pd)
                goto unlock;
 
@@ -8298,7 +8298,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
         * Energy-aware wake-up happens on the lowest sched_domain starting
         * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
         */
-       sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
+       sd = rcu_dereference_all(*this_cpu_ptr(&sd_asym_cpucapacity));
        while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
                sd = sd->parent;
        if (!sd)
@@ -9305,7 +9305,7 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
  */
 static long migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
 {
-       struct numa_group *numa_group = rcu_dereference(p->numa_group);
+       struct numa_group *numa_group = rcu_dereference_all(p->numa_group);
        unsigned long src_weight, dst_weight;
        int src_nid, dst_nid, dist;
 
@@ -10985,7 +10985,7 @@ static void update_idle_cpu_scan(struct lb_env *env,
        if (env->sd->span_weight != llc_weight)
                return;
 
-       sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
+       sd_share = rcu_dereference_all(per_cpu(sd_llc_shared, env->dst_cpu));
        if (!sd_share)
                return;
 
@@ -11335,7 +11335,7 @@ static struct sched_group *sched_balance_find_src_group(struct lb_env *env)
                goto force_balance;
 
        if (!is_rd_overutilized(env->dst_rq->rd) &&
-           rcu_dereference(env->dst_rq->rd->pd))
+           rcu_dereference_all(env->dst_rq->rd->pd))
                goto out_balanced;
 
        /* ASYM feature bypasses nice load balance check */
@@ -12424,7 +12424,7 @@ static void nohz_balancer_kick(struct rq *rq)
 
        rcu_read_lock();
 
-       sd = rcu_dereference(rq->sd);
+       sd = rcu_dereference_all(rq->sd);
        if (sd) {
                /*
                 * If there's a runnable CFS task and the current CPU has reduced
@@ -12436,7 +12436,7 @@ static void nohz_balancer_kick(struct rq *rq)
                }
        }
 
-       sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
+       sd = rcu_dereference_all(per_cpu(sd_asym_packing, cpu));
        if (sd) {
                /*
                 * When ASYM_PACKING; see if there's a more preferred CPU
@@ -12454,7 +12454,7 @@ static void nohz_balancer_kick(struct rq *rq)
                }
        }
 
-       sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
+       sd = rcu_dereference_all(per_cpu(sd_asym_cpucapacity, cpu));
        if (sd) {
                /*
                 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
@@ -12475,7 +12475,7 @@ static void nohz_balancer_kick(struct rq *rq)
                goto unlock;
        }
 
-       sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+       sds = rcu_dereference_all(per_cpu(sd_llc_shared, cpu));
        if (sds) {
                /*
                 * If there is an imbalance between LLC domains (IOW we could
@@ -12507,7 +12507,7 @@ static void set_cpu_sd_state_busy(int cpu)
        struct sched_domain *sd;
 
        rcu_read_lock();
-       sd = rcu_dereference(per_cpu(sd_llc, cpu));
+       sd = rcu_dereference_all(per_cpu(sd_llc, cpu));
 
        if (!sd || !sd->nohz_idle)
                goto unlock;
@@ -12537,7 +12537,7 @@ static void set_cpu_sd_state_idle(int cpu)
        struct sched_domain *sd;
 
        rcu_read_lock();
-       sd = rcu_dereference(per_cpu(sd_llc, cpu));
+       sd = rcu_dereference_all(per_cpu(sd_llc, cpu));
 
        if (!sd || sd->nohz_idle)
                goto unlock;
@@ -13915,7 +13915,7 @@ void show_numa_stats(struct task_struct *p, struct seq_file *m)
        struct numa_group *ng;
 
        rcu_read_lock();
-       ng = rcu_dereference(p->numa_group);
+       ng = rcu_dereference_all(p->numa_group);
        for_each_online_node(node) {
                if (p->numa_faults) {
                        tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 2c0a4eaf02de19a3b21d557df8631c6215486693..67cff7d6cc2ff1d4d7f13bdea8e49f7bf472227a 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2011,7 +2011,7 @@ queue_balance_callback(struct rq *rq,
 }
 
 #define rcu_dereference_sched_domain(p) \
-       rcu_dereference_check((p), lockdep_is_held(&sched_domains_mutex))
+       rcu_dereference_all_check((p), lockdep_is_held(&sched_domains_mutex))
 
 /*
  * The domain tree (rq->sd) is protected by RCU's quiescent state transition.