[PATCH tip/core/rcu 13/14] rcu: Split RCU core processing out of __call_rcu()

Paul E. McKenney
2012-06-15T20:13:51Z

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

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>
---
kernel/rcutree.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 9419ebf..6940a81 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1858,9 +1858,11 @@ 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;
@@ -1905,10 +1907,8 @@ __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.
@@ -1941,6 +1941,49 @@ __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);
}

--
1.7.8