linux-kernel - [tip: sched/core] sched/smt: Fix unbalance sched_smt

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Message-ID: <172224924949.2215.7548335269199359250.tip-bot2@tip-bot2>
Date: Mon, 29 Jul 2024 10:34:09 -0000
From: "tip-bot2 for Yang Yingliang" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: stable@...nel.org, Yang Yingliang <yangyingliang@...wei.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Chen Yu <yu.c.chen@...el.com>, Tim Chen <tim.c.chen@...ux.intel.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/smt: Fix unbalance sched_smt_present dec/inc

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

Commit-ID:     e22f910a26cc2a3ac9c66b8e935ef2a7dd881117
Gitweb:        https://git.kernel.org/tip/e22f910a26cc2a3ac9c66b8e935ef2a7dd881117
Author:        Yang Yingliang <yangyingliang@...wei.com>
AuthorDate:    Wed, 03 Jul 2024 11:16:08 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 29 Jul 2024 12:22:32 +02:00

sched/smt: Fix unbalance sched_smt_present dec/inc

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")
Cc: stable@...nel.org
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Chen Yu <yu.c.chen@...el.com>
Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
Link: https://lore.kernel.org/r/20240703031610.587047-3-yangyingliang@huaweicloud.com
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index acc04ed..949473e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8009,6 +8009,7 @@ 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);