linux-kernel - [PATCH 2/4] sched/smt: fix unbalance sched_smt

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Message-Id: <20240703031610.587047-3-yangyingliang@huaweicloud.com>
Date: Wed,  3 Jul 2024 11:16:08 +0800
From: Yang Yingliang <yangyingliang@...weicloud.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	bristot@...hat.com,
	vschneid@...hat.com,
	tglx@...utronix.de,
	yu.c.chen@...el.com,
	tim.c.chen@...ux.intel.com,
	yangyingliang@...wei.com,
	liwei391@...wei.com
Subject: [PATCH 2/4] sched/smt: fix unbalance sched_smt_present dec/inc

From: Yang Yingliang <yangyingliang@...wei.com>

I got the following warn report while doing stress test:

jump label: negative count!
WARNING: CPU: 3 PID: 38 at kernel/jump_label.c:263 static_key_slow_try_dec+0x9d/0xb0
Call Trace:
 <TASK>
 __static_key_slow_dec_cpuslocked+0x16/0x70
 sched_cpu_deactivate+0x26e/0x2a0
 cpuhp_invoke_callback+0x3ad/0x10d0
 cpuhp_thread_fun+0x3f5/0x680
 smpboot_thread_fn+0x56d/0x8d0
 kthread+0x309/0x400
 ret_from_fork+0x41/0x70
 ret_from_fork_asm+0x1b/0x30
 </TASK>

Because when cpuset_cpu_inactive() fails in sched_cpu_deactivate(),
the cpu offline failed, but sched_smt_present is decremented before
calling sched_cpu_deactivate(), it leads to unbalanced dec/inc, so
fix it by incrementing sched_smt_present in the error path.

Fixes: c5511d03ec09 ("sched/smt: Make sched_smt_present track topology")
Reviewed-by: Chen Yu <yu.c.chen@...el.com>
Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 880c4c03ef8a..5cff01046685 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9768,6 +9768,7 @@ int sched_cpu_deactivate(unsigned int cpu)
 	sched_update_numa(cpu, false);
 	ret = cpuset_cpu_inactive(cpu);
 	if (ret) {
+		sched_smt_present_inc(cpu);
 		balance_push_set(cpu, false);
 		set_cpu_active(cpu, true);
 		sched_update_numa(cpu, true);
-- 
2.25.1