Subject: Re: [PATCH v6 8/9] mm: multigenerational lru: user interface

From: Yu Zhao <[email-masked]>
Date: Thu, 13 Jan 2022 16:02:15 -0700

On Thu, Jan 13, 2022 at 04:01:31PM +0530, Aneesh Kumar K.V wrote:
> Yu Zhao <[email-masked]> writes:
> 
> > Add /sys/kernel/mm/lru_gen/enabled as a runtime kill switch.
> 
> 
> Got the below lockdep warning while using the above kill/enable switch
> 
> 
> [   84.252952] ======================================================
> [   84.253012] WARNING: possible circular locking dependency detected
> [   84.253074] 5.16.0-rc8-16204-g1cdcf1120b31 #511 Not tainted
> [   84.253135] ------------------------------------------------------
> [   84.253194] bash/2862 is trying to acquire lock:
> [   84.253243] c0000000021ff740 (cgroup_mutex){+.+.}-{3:3}, at: store_enable+0x80/0x1510
> [   84.253340]
>                but task is already holding lock:
> [   84.253410] c000000002221348 (mem_hotplug_lock){++++}-{0:0}, at: mem_hotplug_begin+0x30/0x50
> [   84.253503]
>                which lock already depends on the new lock.
> 
> [   84.255933] Chain exists of:
>                  cgroup_mutex --> cpu_hotplug_lock --> mem_hotplug_lock

Thanks. Will reverse the order between mem_hotplug_lock and
cgroup_mutex in the next spin.

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