linux-kernel - [PATCH] x86/resctrl: fix an imbalance in domain_remove

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Message-Id: <20191208041318.3702-1-cai@lca.pw>
Date:   Sat,  7 Dec 2019 23:13:18 -0500
From:   Qian Cai <cai@....pw>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     reinette.chatre@...el.com, fenghua.yu@...el.com, hpa@...or.com,
        john.stultz@...aro.org, sboyd@...nel.org, tony.luck@...el.com,
        tj@...nel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH] x86/resctrl: fix an imbalance in domain_remove_cpu

domain_add_cpu() calls domain_setup_mon_state() only when r->mon_capable
is true where it will initialize d->mbm_over. However,
domain_remove_cpu() calls cancel_delayed_work(&d->mbm_over) without
checking r->mon_capable. Hence, it triggers a debugobjects warning when
offlining CPUs because those timer debugobjects are never initialized.

ODEBUG: assert_init not available (active state 0) object type:
timer_list hint: 0x0
WARNING: CPU: 143 PID: 789 at lib/debugobjects.c:484
debug_print_object+0xfe/0x140
Hardware name: HP Synergy 680 Gen9/Synergy 680 Gen9 Compute Module, BIOS
I40 05/23/2018
RIP: 0010:debug_print_object+0xfe/0x140
Call Trace:
debug_object_assert_init+0x1f5/0x240
del_timer+0x6f/0xf0
try_to_grab_pending+0x42/0x3c0
cancel_delayed_work+0x7d/0x150
resctrl_offline_cpu+0x3c0/0x520
cpuhp_invoke_callback+0x197/0x1120
cpuhp_thread_fun+0x252/0x2f0
smpboot_thread_fn+0x255/0x440
kthread+0x1e6/0x210
ret_from_fork+0x3a/0x50

Fixes: e33026831bdb ("x86/intel_rdt/mbm: Handle counter overflow")
Signed-off-by: Qian Cai <cai@....pw>
---
 arch/x86/kernel/cpu/resctrl/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 03eb90d00af0..89049b343c7a 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -618,7 +618,7 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
 		if (static_branch_unlikely(&rdt_mon_enable_key))
 			rmdir_mondata_subdir_allrdtgrp(r, d->id);
 		list_del(&d->list);
-		if (is_mbm_enabled())
+		if (r->mon_capable && is_mbm_enabled())
 			cancel_delayed_work(&d->mbm_over);
 		if (is_llc_occupancy_enabled() &&  has_busy_rmid(r, d)) {
 			/*
-- 
2.21.0 (Apple Git-122.2)