From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 18 Aug 2020 08:48:17 +0000 (+0200)
Subject: sched/fair: Exclude the current CPU from find_new_ilb()
X-Git-Tag: v5.11-rc1~174^2~37
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=45da7a2b0af8fa29dff2e6ba8926322068350fce;p=thirdparty%2Fkernel%2Flinux.git

sched/fair: Exclude the current CPU from find_new_ilb()

It is possible for find_new_ilb() to select the current CPU, however,
this only happens from newidle balancing, in which case need_resched()
will be true, and consequently nohz_csd_func() will not trigger the
softirq.

Exclude the current CPU from becoming an ILB target.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b9368d123451d..cd9a37c0601bb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10056,6 +10056,10 @@ static inline int find_new_ilb(void)
 
 	for_each_cpu_and(ilb, nohz.idle_cpus_mask,
 			      housekeeping_cpumask(HK_FLAG_MISC)) {
+
+		if (ilb == smp_processor_id())
+			continue;
+
 		if (idle_cpu(ilb))
 			return ilb;
 	}