rcu: Create transitive rnp->lock acquisition functions

Providing RCU's memory-ordering guarantees requires that the rcu_node
tree's locking provide transitive memory ordering, which the Linux kernel's
spinlocks currently do not provide unless smp_mb__after_unlock_lock()
is used.  Having a separate smp_mb__after_unlock_lock() after each and
every lock acquisition is error-prone, hard to read, and a bit annoying,
so this commit provides wrapper functions that pull in the
smp_mb__after_unlock_lock() invocations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 26 insertions, 52 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f07343b54fe5..daf17e248757 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1534,10 +1534,8 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
          * hold it, acquire the root rcu_node structure's lock in order to
          * start one (if needed).
          */
-        if (rnp != rnp_root) {
-                raw_spin_lock(&rnp_root->lock);
-                smp_mb__after_unlock_lock();
-        }
+        if (rnp != rnp_root)
+                raw_spin_lock_rcu_node(rnp_root);
 
         /*
          * Get a new grace-period number.  If there really is no grace
@@ -1786,11 +1784,10 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
         if ((rdp->gpnum == READ_ONCE(rnp->gpnum) &&
              rdp->completed == READ_ONCE(rnp->completed) &&
              !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
-            !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
+            !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
                 local_irq_restore(flags);
                 return;
         }
-        smp_mb__after_unlock_lock();
         needwake = __note_gp_changes(rsp, rnp, rdp);
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
         if (needwake)
@@ -1814,8 +1811,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         WRITE_ONCE(rsp->gp_activity, jiffies);
-        raw_spin_lock_irq(&rnp->lock);
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_irq_rcu_node(rnp);
         if (!READ_ONCE(rsp->gp_flags)) {
                 /* Spurious wakeup, tell caller to go back to sleep.  */
                 raw_spin_unlock_irq(&rnp->lock);
@@ -1847,8 +1843,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
          */
         rcu_for_each_leaf_node(rsp, rnp) {
                 rcu_gp_slow(rsp, gp_preinit_delay);
-                raw_spin_lock_irq(&rnp->lock);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irq_rcu_node(rnp);
                 if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
                     !rnp->wait_blkd_tasks) {
                         /* Nothing to do on this leaf rcu_node structure. */
@@ -1904,8 +1899,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
          */
         rcu_for_each_node_breadth_first(rsp, rnp) {
                 rcu_gp_slow(rsp, gp_init_delay);
-                raw_spin_lock_irq(&rnp->lock);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irq_rcu_node(rnp);
                 rdp = this_cpu_ptr(rsp->rda);
                 rcu_preempt_check_blocked_tasks(rnp);
                 rnp->qsmask = rnp->qsmaskinit;
@@ -1973,8 +1967,7 @@ static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time)
         }
         /* Clear flag to prevent immediate re-entry. */
         if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
-                raw_spin_lock_irq(&rnp->lock);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irq_rcu_node(rnp);
                 WRITE_ONCE(rsp->gp_flags,
                            READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS);
                 raw_spin_unlock_irq(&rnp->lock);
@@ -1993,8 +1986,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         WRITE_ONCE(rsp->gp_activity, jiffies);
-        raw_spin_lock_irq(&rnp->lock);
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_irq_rcu_node(rnp);
         gp_duration = jiffies - rsp->gp_start;
         if (gp_duration > rsp->gp_max)
                 rsp->gp_max = gp_duration;
@@ -2019,8 +2011,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
          * grace period is recorded in any of the rcu_node structures.
          */
         rcu_for_each_node_breadth_first(rsp, rnp) {
-                raw_spin_lock_irq(&rnp->lock);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irq_rcu_node(rnp);
                 WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
                 WARN_ON_ONCE(rnp->qsmask);
                 WRITE_ONCE(rnp->completed, rsp->gpnum);
@@ -2035,8 +2026,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
                 rcu_gp_slow(rsp, gp_cleanup_delay);
         }
         rnp = rcu_get_root(rsp);
-        raw_spin_lock_irq(&rnp->lock);
-        smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */
+        raw_spin_lock_irq_rcu_node(rnp); /* Order GP before ->completed update. */
         rcu_nocb_gp_set(rnp, nocb);
 
         /* Declare grace period done. */
@@ -2284,8 +2274,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 rnp_c = rnp;
                 rnp = rnp->parent;
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irqsave_rcu_node(rnp, flags);
                 oldmask = rnp_c->qsmask;
         }
 
@@ -2332,8 +2321,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
         gps = rnp->gpnum;
         mask = rnp->grpmask;
         raw_spin_unlock(&rnp->lock);    /* irqs remain disabled. */
-        raw_spin_lock(&rnp_p->lock);    /* irqs already disabled. */
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_rcu_node(rnp_p);  /* irqs already disabled. */
         rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags);
 }
 
@@ -2355,8 +2343,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
         struct rcu_node *rnp;
 
         rnp = rdp->mynode;
-        raw_spin_lock_irqsave(&rnp->lock, flags);
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_irqsave_rcu_node(rnp, flags);
         if ((rdp->cpu_no_qs.b.norm &&
              rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||
             rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||
@@ -2582,8 +2569,7 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
                 rnp = rnp->parent;
                 if (!rnp)
                         break;
-                raw_spin_lock(&rnp->lock); /* irqs already disabled. */
-                smp_mb__after_unlock_lock(); /* GP memory ordering. */
+                raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
                 rnp->qsmaskinit &= ~mask;
                 rnp->qsmask &= ~mask;
                 if (rnp->qsmaskinit) {
@@ -2611,8 +2597,7 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
 
         /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
         mask = rdp->grpmask;
-        raw_spin_lock_irqsave(&rnp->lock, flags);
-        smp_mb__after_unlock_lock();    /* Enforce GP memory-order guarantee. */
+        raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
         rnp->qsmaskinitnext &= ~mask;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
@@ -2809,8 +2794,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
         rcu_for_each_leaf_node(rsp, rnp) {
                 cond_resched_rcu_qs();
                 mask = 0;
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irqsave_rcu_node(rnp, flags);
                 if (rnp->qsmask == 0) {
                         if (rcu_state_p == &rcu_sched_state ||
                             rsp != rcu_state_p ||
@@ -2881,8 +2865,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
         /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
 
         /* Reached the root of the rcu_node tree, acquire lock. */
-        raw_spin_lock_irqsave(&rnp_old->lock, flags);
-        smp_mb__after_unlock_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) {
                 rsp->n_force_qs_lh++;
@@ -3005,8 +2988,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
                 if (!rcu_gp_in_progress(rsp)) {
                         struct rcu_node *rnp_root = rcu_get_root(rsp);
 
-                        raw_spin_lock(&rnp_root->lock);
-                        smp_mb__after_unlock_lock();
+                        raw_spin_lock_rcu_node(rnp_root);
                         needwake = rcu_start_gp(rsp);
                         raw_spin_unlock(&rnp_root->lock);
                         if (needwake)
@@ -3426,8 +3408,7 @@ static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
          * CPUs for the current rcu_node structure up the rcu_node tree.
          */
         rcu_for_each_leaf_node(rsp, rnp) {
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irqsave_rcu_node(rnp, flags);
                 if (rnp->expmaskinit == rnp->expmaskinitnext) {
                         raw_spin_unlock_irqrestore(&rnp->lock, flags);
                         continue;  /* No new CPUs, nothing to do. */
@@ -3447,8 +3428,7 @@ static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
                 rnp_up = rnp->parent;
                 done = false;
                 while (rnp_up) {
-                        raw_spin_lock_irqsave(&rnp_up->lock, flags);
-                        smp_mb__after_unlock_lock();
+                        raw_spin_lock_irqsave_rcu_node(rnp_up, flags);
                         if (rnp_up->expmaskinit)
                                 done = true;
                         rnp_up->expmaskinit |= mask;
@@ -3472,8 +3452,7 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
 
         sync_exp_reset_tree_hotplug(rsp);
         rcu_for_each_node_breadth_first(rsp, rnp) {
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irqsave_rcu_node(rnp, flags);
                 WARN_ON_ONCE(rnp->expmask);
                 rnp->expmask = rnp->expmaskinit;
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -3531,8 +3510,7 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
                 mask = rnp->grpmask;
                 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
                 rnp = rnp->parent;
-                raw_spin_lock(&rnp->lock); /* irqs already disabled */
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_rcu_node(rnp); /* irqs already disabled */
                 WARN_ON_ONCE(!(rnp->expmask & mask));
                 rnp->expmask &= ~mask;
         }
@@ -3549,8 +3527,7 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
 {
         unsigned long flags;
 
-        raw_spin_lock_irqsave(&rnp->lock, flags);
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_irqsave_rcu_node(rnp, flags);
         __rcu_report_exp_rnp(rsp, rnp, wake, flags);
 }
 
@@ -3564,8 +3541,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
 {
         unsigned long flags;
 
-        raw_spin_lock_irqsave(&rnp->lock, flags);
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_irqsave_rcu_node(rnp, flags);
         if (!(rnp->expmask & mask)) {
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
@@ -3708,8 +3684,7 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 
         sync_exp_reset_tree(rsp);
         rcu_for_each_leaf_node(rsp, rnp) {
-                raw_spin_lock_irqsave(&rnp->lock, flags);
-                smp_mb__after_unlock_lock();
+                raw_spin_lock_irqsave_rcu_node(rnp, flags);
 
                 /* Each pass checks a CPU for identity, offline, and idle. */
                 mask_ofl_test = 0;
@@ -4198,8 +4173,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
          */
         rnp = rdp->mynode;
         mask = rdp->grpmask;
-        raw_spin_lock(&rnp->lock);              /* irqs already disabled. */
-        smp_mb__after_unlock_lock();
+        raw_spin_lock_rcu_node(rnp);            /* irqs already disabled. */
         rnp->qsmaskinitnext |= mask;
         rnp->expmaskinitnext |= mask;
         if (!rdp->beenonline)