rcu: Eliminate quiescent-state and grace-period-nonstart use of rsp

Now that there is only one rcu_state structure, there is less point in
maintaining a pointer to it.  This commit therefore replaces rsp with
&rcu_state in rcu_report_qs_rnp(), force_quiescent_state(), and
rcu_check_gp_start_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 46bdb52..f329282 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2198,7 +2198,6 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
 {
        unsigned long oldmask = 0;
        struct rcu_node *rnp_c;
-       struct rcu_state __maybe_unused *rsp = &rcu_state;
 
        raw_lockdep_assert_held_rcu_node(rnp);
 
@@ -2217,7 +2216,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
                WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
                             rcu_preempt_blocked_readers_cgp(rnp));
                rnp->qsmask &= ~mask;
-               trace_rcu_quiescent_state_report(rsp->name, rnp->gp_seq,
+               trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq,
                                                 mask, rnp->qsmask, rnp->level,
                                                 rnp->grplo, rnp->grphi,
                                                 !!rnp->gp_tasks);
@@ -2624,12 +2623,11 @@ static void force_quiescent_state(void)
        bool ret;
        struct rcu_node *rnp;
        struct rcu_node *rnp_old = NULL;
-       struct rcu_state *rsp = &rcu_state;
 
        /* Funnel through hierarchy to reduce memory contention. */
        rnp = __this_cpu_read(rcu_data.mynode);
        for (; rnp != NULL; rnp = rnp->parent) {
-               ret = (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
+               ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
                      !raw_spin_trylock(&rnp->fqslock);
                if (rnp_old != NULL)
                        raw_spin_unlock(&rnp_old->fqslock);
@@ -2642,11 +2640,12 @@ static void force_quiescent_state(void)
        /* Reached the root of the rcu_node tree, acquire lock. */
        raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
        raw_spin_unlock(&rnp_old->fqslock);
-       if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
+       if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
                raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
                return;  /* Someone beat us to it. */
        }
-       WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
+       WRITE_ONCE(rcu_state.gp_flags,
+                  READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
        raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
        rcu_gp_kthread_wake();
 }
@@ -2662,15 +2661,14 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp)
        unsigned long flags;
        unsigned long j;
        struct rcu_node *rnp_root = rcu_get_root();
-       struct rcu_state *rsp = &rcu_state;
        static atomic_t warned = ATOMIC_INIT(0);
 
        if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() ||
            ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed))
                return;
        j = jiffies; /* Expensive access, and in common case don't get here. */
-       if (time_before(j, READ_ONCE(rsp->gp_req_activity) + gpssdelay) ||
-           time_before(j, READ_ONCE(rsp->gp_activity) + gpssdelay) ||
+       if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
+           time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
            atomic_read(&warned))
                return;
 
@@ -2678,8 +2676,8 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp)
        j = jiffies;
        if (rcu_gp_in_progress() ||
            ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
-           time_before(j, READ_ONCE(rsp->gp_req_activity) + gpssdelay) ||
-           time_before(j, READ_ONCE(rsp->gp_activity) + gpssdelay) ||
+           time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
+           time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
            atomic_read(&warned)) {
                raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
                return;
@@ -2691,19 +2689,19 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp)
        j = jiffies;
        if (rcu_gp_in_progress() ||
            ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
-           time_before(j, rsp->gp_req_activity + gpssdelay) ||
-           time_before(j, rsp->gp_activity + gpssdelay) ||
+           time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
+           time_before(j, rcu_state.gp_activity + gpssdelay) ||
            atomic_xchg(&warned, 1)) {
                raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
                raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
                return;
        }
        pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n",
-                __func__, (long)READ_ONCE(rsp->gp_seq),
+                __func__, (long)READ_ONCE(rcu_state.gp_seq),
                 (long)READ_ONCE(rnp_root->gp_seq_needed),
-                j - rsp->gp_req_activity, j - rsp->gp_activity,
-                rsp->gp_flags, rsp->gp_state, rsp->name,
-                rsp->gp_kthread ? rsp->gp_kthread->state : 0x1ffffL);
+                j - rcu_state.gp_req_activity, j - rcu_state.gp_activity,
+                rcu_state.gp_flags, rcu_state.gp_state, rcu_state.name,
+                rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL);
        WARN_ON(1);
        if (rnp_root != rnp)
                raw_spin_unlock_rcu_node(rnp_root);