linux-kernel - Re: resctrl mount fail on v6.13-rc1

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Message-ID: <Z0441XN_KoCP-fNz@agluck-desk3>
Date: Mon, 2 Dec 2024 14:46:45 -0800
From: "Luck, Tony" <tony.luck@...el.com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	Babu Moger <babu.moger@....com>, linux-kernel@...r.kernel.org
Subject: Re: resctrl mount fail on v6.13-rc1

On Mon, Dec 02, 2024 at 02:26:48PM -0800, Reinette Chatre wrote:
> Hi Tony,
> 
> On 12/2/24 1:42 PM, Luck, Tony wrote:
> > Anyone better a decoding lockdep dumps then me make sense of this?
> > 
> > All I did was build v6.13-rc1 with (among others)
> > 
> > CONFIG_PROVE_LOCKING=y
> > CONFIG_PROVE_RAW_LOCK_NESTING=y
> > CONFIG_PROVE_RCU=y
> > 
> > and then mount the resctrl filesystem:
> > 
> > $ sudo mount -t resctrl resctrl /sys/fs/resctrl
> > 
> > There are only trivial changes to the resctrl code between
> > v6.12 (which works) and v6.13-rc1:
> > 
> > $ git log --oneline v6.13-rc1 ^v6.12 -- arch/x86/kernel/cpu/resctrl
> > 5a4b3fbb4849 Merge tag 'x86_cache_for_v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
> > 9bce6e94c4b3 x86/resctrl: Support Sub-NUMA cluster mode SNC6
> > 29eaa7958367 x86/resctrl: Slightly clean-up mbm_config_show()
> > 
> > So something in kernfs? Or the way resctrl uses kernfs?
> 
> I am not seeing this but that may be because I am not testing with
> selinux enabled. My test kernel has:
> # CONFIG_SECURITY_SELINUX is not set

I did have SELINUX configured. Disabling this CONFIG option
makes the lockdep splat go away.
> 
> I am also not running with any btrfs filesystems. 

My root and home filesystems are btrfs, so difficult to
check if this is also connected.
> 
> Is this your usual setup in which you are seeing this the first time? Is it
> perhaps possible for you to bisect?
> 
> The subject states "resctrl mount fail" - could you please confirm if
> resctrl cannot be mounted in addition to the lockdep warning?

The filesystem did get mounted despite all the lockdep noise.

> 
> Reinette

-Tony