linux-kernel - Re: [PATCH v2 0/2] Lock and Pointer guards

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Date:   Tue, 30 May 2023 11:26:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     keescook@...omium.org, gregkh@...uxfoundation.org,
        pbonzini@...hat.com, linux-kernel@...r.kernel.org,
        ojeda@...nel.org, ndesaulniers@...gle.com, mingo@...hat.com,
        will@...nel.org, longman@...hat.com, boqun.feng@...il.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        joel@...lfernandes.org, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        rcu@...r.kernel.org, tj@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH v2 0/2] Lock and Pointer guards

On Sat, May 27, 2023 at 12:18:04PM -0700, Linus Torvalds wrote:

> And before you say "unlock order doesn't matter" - that's actually not
> true. Unlock order does matter when you have things like
> "spin_lock_irq()" where the irq-off region then protects other locks
> too.

So I had already verified that GCC keeps them ordered, I see the
subthread with Ian and the documentation update request -- so all good
there.

Also, lockdep would scream bloody murder if you get that wrong, so I
can certainly add something to the selftests that would detect this.