rcu: Split RCU core processing out of __call_rcu()

The __call_rcu() function is a bit overweight, so this commit splits
it into actual enqueuing of and accounting for the callback (__call_rcu())
and associated RCU-core processing (__call_rcu_core()).

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 49 insertions, 41 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ceaa95923a87..70c4da7d2a97 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1861,45 +1861,12 @@ static void invoke_rcu_core(void)
         raise_softirq(RCU_SOFTIRQ);
 }
 
-static void
-__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
-           struct rcu_state *rsp, bool lazy)
+/*
+ * Handle any core-RCU processing required by a call_rcu() invocation.
+ */
+static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
+                            struct rcu_head *head, unsigned long flags)
 {
-        unsigned long flags;
-        struct rcu_data *rdp;
-
-        WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
-        debug_rcu_head_queue(head);
-        head->func = func;
-        head->next = NULL;
-
-        smp_mb(); /* Ensure RCU update seen before callback registry. */
-
-        /*
-         * Opportunistically note grace-period endings and beginnings.
-         * Note that we might see a beginning right after we see an
-         * end, but never vice versa, since this CPU has to pass through
-         * a quiescent state betweentimes.
-         */
-        local_irq_save(flags);
-        rdp = this_cpu_ptr(rsp->rda);
-
-        /* Add the callback to our list. */
-        ACCESS_ONCE(rdp->qlen)++;
-        if (lazy)
-                rdp->qlen_lazy++;
-        else
-                rcu_idle_count_callbacks_posted();
-        smp_mb();  /* Count before adding callback for rcu_barrier(). */
-        *rdp->nxttail[RCU_NEXT_TAIL] = head;
-        rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
-
-        if (__is_kfree_rcu_offset((unsigned long)func))
-                trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
-                                         rdp->qlen_lazy, rdp->qlen);
-        else
-                trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
-
         /*
          * If called from an extended quiescent state, invoke the RCU
          * core in order to force a re-evaluation of RCU's idleness.
@@ -1908,10 +1875,8 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
                 invoke_rcu_core();
 
         /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
-        if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) {
-                local_irq_restore(flags);
+        if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
                 return;
-        }
 
         /*
          * Force the grace period if too many callbacks or too long waiting.
@@ -1944,6 +1909,49 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
                 }
         } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
                 force_quiescent_state(rsp, 1);
+}
+
+static void
+__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
+           struct rcu_state *rsp, bool lazy)
+{
+        unsigned long flags;
+        struct rcu_data *rdp;
+
+        WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
+        debug_rcu_head_queue(head);
+        head->func = func;
+        head->next = NULL;
+
+        smp_mb(); /* Ensure RCU update seen before callback registry. */
+
+        /*
+         * Opportunistically note grace-period endings and beginnings.
+         * Note that we might see a beginning right after we see an
+         * end, but never vice versa, since this CPU has to pass through
+         * a quiescent state betweentimes.
+         */
+        local_irq_save(flags);
+        rdp = this_cpu_ptr(rsp->rda);
+
+        /* Add the callback to our list. */
+        ACCESS_ONCE(rdp->qlen)++;
+        if (lazy)
+                rdp->qlen_lazy++;
+        else
+                rcu_idle_count_callbacks_posted();
+        smp_mb();  /* Count before adding callback for rcu_barrier(). */
+        *rdp->nxttail[RCU_NEXT_TAIL] = head;
+        rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+
+        if (__is_kfree_rcu_offset((unsigned long)func))
+                trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
+                                         rdp->qlen_lazy, rdp->qlen);
+        else
+                trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
+
+        /* Go handle any RCU core processing required. */
+        __call_rcu_core(rsp, rdp, head, flags);
         local_irq_restore(flags);
 }