linux-kernel - Re: [PATCH 4/4] lockdep: make MAX_LOCK

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Message-ID: <20170928092600.qvehxzikcjr65hvw@hirez.programming.kicks-ass.net>
Date:   Thu, 28 Sep 2017 11:26:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Govindarajulu Varadarajan <gvaradar@...co.com>
Cc:     benve@...co.com, bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, jlbec@...lplan.org, hch@....de,
        mingo@...hat.com
Subject: Re: [PATCH 4/4] lockdep: make MAX_LOCK_DEPTH configurable from
 Kconfig

On Wed, Sep 27, 2017 at 02:42:20PM -0700, Govindarajulu Varadarajan wrote:
> Make MAX_LOCK_DEPTH configurable. It is set to 48 right now. Number of
> VFs under a PCI pf bus can exceed 48 and this disables lockdep.
> 
> lockdep currently allows max of 63 held_locks.

But why a config knob? Why not just raise the number to 64
unconditionally? And is that sufficient; you only state 48 is
insufficient, you don't actually state the VF limit.