[v2] rcu/nocb: Delete local variable 'need_rcu_nocb_mask' in rcu_init_nohz()

Commit Message

Leizhen (ThunderTown) June 7, 2022, 6:37 a.m. UTC

...
bool need_rcu_nocb_mask = false;

//#if defined(CONFIG_NO_HZ_FULL)
if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask))
        need_rcu_nocb_mask = true;      <----	//Move it here
//#endif                                     |
                                             |
if (need_rcu_nocb_mask) {                    |  //Can only be true above
         ...                            -----
}

The local variable 'need_rcu_nocb_mask' is true only if CONFIG_NO_HZ_FULL
is defined. So branch "if (need_rcu_nocb_mask)" can be moved within the
scope of "#if defined(CONFIG_NO_HZ_FULL)". At this point, using variable
'need_rcu_nocb_mask' is not necessary, so delete it.

No functional changes, but the code looks a little more concise.

The kernel built with CONFIG_NO_HZ_FULL=n and CONFIG_RCU_NOCB_CPU=y ran
continuously for a whole day, no errors were reported.

Signed-off-by: Zhen Lei <[e-mail]>
---
 kernel/rcu/tree_nocb.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

v1 --> v2:
Update commit message.

Patch

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 46694e13398a3ee..e7fe99eb58972a6 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1154,15 +1154,10 @@  EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
 void __init rcu_init_nohz(void)
 {
 	int cpu;
-	bool need_rcu_nocb_mask = false;
 	struct rcu_data *rdp;
 
 #if defined(CONFIG_NO_HZ_FULL)
-	if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask))
-		need_rcu_nocb_mask = true;
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
-	if (need_rcu_nocb_mask) {
+	if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) {
 		if (!cpumask_available(rcu_nocb_mask)) {
 			if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
 				pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
@@ -1171,6 +1166,7 @@  void __init rcu_init_nohz(void)
 		}
 		rcu_state.nocb_is_setup = true;
 	}
+#endif /* #if defined(CONFIG_NO_HZ_FULL) */
 
 	if (!rcu_state.nocb_is_setup)
 		return;