linux-kernel - Re: [PATCH v4 04/10] mm/vma: add+use vma lockdep acquire/release defines

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Message-ID: <e09d5642-a9c7-4b72-9646-ec994e57170d@lucifer.local>
Date: Wed, 28 Jan 2026 11:31:41 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...nel.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Shakeel Butt <shakeel.butt@...ux.dev>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-rt-devel@...ts.linux.dev, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>,
        Clark Williams <clrkwllms@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v4 04/10] mm/vma: add+use vma lockdep acquire/release
 defines

On Wed, Jan 28, 2026 at 12:18:32PM +0100, Sebastian Andrzej Siewior wrote:
> On 2026-01-23 20:12:14 [+0000], Lorenzo Stoakes wrote:
> > The code is littered with inscrutable and duplicative lockdep incantations,
> > replace these with defines which explain what is going on and add
> > commentary to explain what we're doing.
> >
> > If lockdep is disabled these become no-ops. We must use defines so _RET_IP_
> > remains meaningful.
> >
> > These are self-documenting and aid readability of the code.
> >
> > Additionally, instead of using the confusing rwsem_*() form for something
> > that is emphatically not an rwsem, we instead explicitly use
> > lock_[acquired, release]_shared/exclusive() lockdep invocations since we
> > are doing something rather custom here and these make more sense to use.
> >
> > No functional change intended.
>
> This is just "replace rwsem macro with our own macro" which is fine. The
> subject confused me because I expected something new to see ;)

Haha well yeah, I mean it's been a bit of a journey actually, reminding myself
of how we actually use lockdep with the VMA locks and then, in real time,
realising how broken a 'is held' can be, so in general I think we got to a good
place!

>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Thanks!

>
> Sebastian

Cheers, Lorenzo