linux-kernel - Re: [PATCH v2 09/17] debugobjects: Make object hash locks nestable terminal locks

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Message-ID: <20181122153302.y5vqovrsaigi6pte@pathway.suse.cz>
Date:   Thu, 22 Nov 2018 16:33:02 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 09/17] debugobjects: Make object hash locks nestable
 terminal locks

On Mon 2018-11-19 13:55:18, Waiman Long wrote:
> By making the object hash locks nestable terminal locks, we can avoid
> a bunch of unnecessary lockdep validations as well as saving space
> in the lockdep tables.

Please, explain which terminal lock might be nested.

Hmm, it would hide eventual nesting of other terminal locks.
It might reduce lockdep reliability. I wonder if the space
optimization is worth it.

Finally, it might be good to add a short explanation what (nested)
terminal locks mean into each commit. It would help people to
understand the effect without digging into the lockdep code, ...

Best Regards,
Petr