[PATCH] rcu: Improve tree_plugin.h comments and add code cleanups

[PATCH] rcu: Improve tree_plugin.h comments and add code cleanups

[Zhouyi Zhou]

This commit cleans up some comments and code in kernel/rcu/tree_plugin.h.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
---
Hi Paul,

I perform some comments and code cleans up in kernel/rcu/tree_plugin.h
while learning RCU.

Thanks
Zhouyi
--
 kernel/rcu/tree_plugin.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index d070059163d7..dde7fa17ae2b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -16,7 +16,7 @@
 static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
 {
 	/*
-	 * In order to read the offloaded state of an rdp is a safe
+	 * In order to read the offloaded state of an rdp in a safe
 	 * and stable way and prevent from its value to be changed
 	 * under us, we must either hold the barrier mutex, the cpu
 	 * hotplug lock (read or write) or the nocb lock. Local
@@ -56,7 +56,7 @@ static void __init rcu_bootup_announce_oddness(void)
 	if (IS_ENABLED(CONFIG_PROVE_RCU))
 		pr_info("\tRCU lockdep checking is enabled.\n");
 	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
-		pr_info("\tRCU strict (and thus non-scalable) grace periods enabled.\n");
+		pr_info("\tRCU strict (and thus non-scalable) grace periods are enabled.\n");
 	if (RCU_NUM_LVLS >= 4)
 		pr_info("\tFour(or more)-level hierarchy is enabled.\n");
 	if (RCU_FANOUT_LEAF != 16)
@@ -88,13 +88,13 @@ static void __init rcu_bootup_announce_oddness(void)
 	if (rcu_kick_kthreads)
 		pr_info("\tKick kthreads if too-long grace period.\n");
 	if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD))
-		pr_info("\tRCU callback double-/use-after-free debug enabled.\n");
+		pr_info("\tRCU callback double-/use-after-free debug is enabled.\n");
 	if (gp_preinit_delay)
 		pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay);
 	if (gp_init_delay)
 		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
 	if (gp_cleanup_delay)
-		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
+		pr_info("\tRCU debug GP cleanup slowdown %d jiffies.\n", gp_cleanup_delay);
 	if (!use_softirq)
 		pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n");
 	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
@@ -1154,7 +1154,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
 /*
  * Create an RCU-boost kthread for the specified node if one does not
  * already exist.  We only create this kthread for preemptible RCU.
- * Returns zero if all is well, a negated errno otherwise.
  */
 static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
 {
@@ -1456,7 +1455,7 @@ static void rcu_cleanup_after_idle(void)
  * CPU unless the grace period has extended for too long.
  *
  * This code relies on the fact that all NO_HZ_FULL CPUs are also
- * CONFIG_RCU_NOCB_CPU CPUs.
+ * RCU_NOCB_CPU CPUs.
  */
 static bool rcu_nohz_full_cpu(void)
 {
-- 
2.25.1

Re: [PATCH] rcu: Improve tree_plugin.h comments and add code cleanups

[Paul E. McKenney]

On Sun, Oct 24, 2021 at 08:36:34AM +0800, Zhouyi Zhou wrote:
> This commit cleans up some comments and code in kernel/rcu/tree_plugin.h.
> 
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
> ---
> Hi Paul,
> 
> I perform some comments and code cleans up in kernel/rcu/tree_plugin.h
> while learning RCU.

Good eyes, queued and pushed, thank you!

A couple of comments below.

							Thanx, Paul

> Thanks
> Zhouyi
> --
>  kernel/rcu/tree_plugin.h | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index d070059163d7..dde7fa17ae2b 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -16,7 +16,7 @@
>  static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
>  {
>  	/*
> -	 * In order to read the offloaded state of an rdp is a safe
> +	 * In order to read the offloaded state of an rdp in a safe
>  	 * and stable way and prevent from its value to be changed
>  	 * under us, we must either hold the barrier mutex, the cpu
>  	 * hotplug lock (read or write) or the nocb lock. Local
> @@ -56,7 +56,7 @@ static void __init rcu_bootup_announce_oddness(void)
>  	if (IS_ENABLED(CONFIG_PROVE_RCU))
>  		pr_info("\tRCU lockdep checking is enabled.\n");
>  	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
> -		pr_info("\tRCU strict (and thus non-scalable) grace periods enabled.\n");
> +		pr_info("\tRCU strict (and thus non-scalable) grace periods are enabled.\n");

Although the original is a correct abbreviation by common usage (witness
"Hyperdrive module enabled!" in some science fiction movies or similar),
it certainly does not hurt to move towards standard usage.  So I took
this change.

>  	if (RCU_NUM_LVLS >= 4)
>  		pr_info("\tFour(or more)-level hierarchy is enabled.\n");
>  	if (RCU_FANOUT_LEAF != 16)
> @@ -88,13 +88,13 @@ static void __init rcu_bootup_announce_oddness(void)
>  	if (rcu_kick_kthreads)
>  		pr_info("\tKick kthreads if too-long grace period.\n");
>  	if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD))
> -		pr_info("\tRCU callback double-/use-after-free debug enabled.\n");
> +		pr_info("\tRCU callback double-/use-after-free debug is enabled.\n");

And same here.

>  	if (gp_preinit_delay)
>  		pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay);
>  	if (gp_init_delay)
>  		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
>  	if (gp_cleanup_delay)
> -		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
> +		pr_info("\tRCU debug GP cleanup slowdown %d jiffies.\n", gp_cleanup_delay);
>  	if (!use_softirq)
>  		pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n");
>  	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
> @@ -1154,7 +1154,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
>  /*
>   * Create an RCU-boost kthread for the specified node if one does not
>   * already exist.  We only create this kthread for preemptible RCU.
> - * Returns zero if all is well, a negated errno otherwise.
>   */
>  static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
>  {
> @@ -1456,7 +1455,7 @@ static void rcu_cleanup_after_idle(void)
>   * CPU unless the grace period has extended for too long.
>   *
>   * This code relies on the fact that all NO_HZ_FULL CPUs are also
> - * CONFIG_RCU_NOCB_CPU CPUs.
> + * RCU_NOCB_CPU CPUs.
>   */
>  static bool rcu_nohz_full_cpu(void)
>  {
> -- 
> 2.25.1
>