linux-kernel - Re: [PATCH v2] x86/resctrl: fix an imbalance in domain_remove

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Message-ID: <9e7483f2-75cc-afaa-e1ea-287a970d4579@intel.com>
Date:   Wed, 11 Dec 2019 10:02:56 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Qian Cai <cai@....pw>, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de
Cc:     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
Subject: Re: [PATCH v2] x86/resctrl: fix an imbalance in domain_remove_cpu

Hi Qian,

On 12/10/2019 7:30 PM, Qian Cai wrote:
> A system that supports resource monitoring may have multiple resources
> while not all of these resources are capable of monitoring. Monitoring
> related state is initialized only for resources that are capable of
> monitoring and correspondingly this state should subsequently only be
> removed from these resources that are capable of monitoring.
> 
> 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 resulting in an attempt to cancel d->mbm_over on
> all resources, even those that never initialized d->mbm_over because
> they are not capable of monitoring. 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>
> ---

Thank you very much.

Acked-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette