[tip: core/rcu] rcu/tree: Use static initializer for krc.lock

["tip-bot2 for Sebastian Andrzej Siewior" <tip-bot2@xxxxxxxxxxxxx>]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     69f08d3999dbef1553a3332b8055282dd3893b6c
Gitweb:        https://git.kernel.org/tip/69f08d3999dbef1553a3332b8055282dd3893b6c
Author:        Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate:    Mon, 25 May 2020 23:47:51 +02:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 29 Jun 2020 11:59:25 -07:00

rcu/tree: Use static initializer for krc.lock

The per-CPU variable is initialized at runtime in
kfree_rcu_batch_init(). This function is invoked before
'rcu_scheduler_active' is set to 'RCU_SCHEDULER_RUNNING'.
After the initialisation, '->initialized' is to true.

The raw_spin_lock is only acquired if '->initialized' is
set to true. The worqueue item is only used if 'rcu_scheduler_active'
set to RCU_SCHEDULER_RUNNING which happens after initialisation.

Use a static initializer for krc.lock and remove the runtime
initialisation of the lock. Since the lock can now be always
acquired, remove the '->initialized' check.

Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/rcu/tree.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 368bdc4..a42a469 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3002,7 +3002,7 @@ struct kfree_rcu_cpu_work {
  * @lock: Synchronize access to this structure
  * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
  * @monitor_todo: Tracks whether a @monitor_work delayed work is pending
- * @initialized: The @lock and @rcu_work fields have been initialized
+ * @initialized: The @rcu_work fields have been initialized
  * @count: Number of objects for which GP not started
  *
  * This is a per-CPU structure.  The reason that it is not included in
@@ -3022,7 +3022,9 @@ struct kfree_rcu_cpu {
 	int count;
 };
 
-static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc);
+static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
+	.lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
+};
 
 static __always_inline void
 debug_rcu_bhead_unqueue(struct kfree_rcu_bulk_data *bhead)
@@ -3042,8 +3044,7 @@ krc_this_cpu_lock(unsigned long *flags)
 
 	local_irq_save(*flags);	// For safely calling this_cpu_ptr().
 	krcp = this_cpu_ptr(&krc);
-	if (likely(krcp->initialized))
-		raw_spin_lock(&krcp->lock);
+	raw_spin_lock(&krcp->lock);
 
 	return krcp;
 }
@@ -3051,8 +3052,7 @@ krc_this_cpu_lock(unsigned long *flags)
 static inline void
 krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
 {
-	if (likely(krcp->initialized))
-		raw_spin_unlock(&krcp->lock);
+	raw_spin_unlock(&krcp->lock);
 	local_irq_restore(flags);
 }
 
@@ -4278,7 +4278,6 @@ static void __init kfree_rcu_batch_init(void)
 	for_each_possible_cpu(cpu) {
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
 
-		raw_spin_lock_init(&krcp->lock);
 		for (i = 0; i < KFREE_N_BATCHES; i++) {
 			INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
 			krcp->krw_arr[i].krcp = krcp;