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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Fri, 28 Jan 2022 17:04:13 +0100
Message-ID: <CAHmME9qBj2gL=spp3AUEo-Ri4r0KQq-KrR-f6dG++xXQvzcA7A@mail.gmail.com>
Subject: Re: "BUG: Invalid wait context" in invalidate_batched_entropy
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     =?UTF-8?Q?Jonathan_Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>,
        Andy Lutomirski <luto@amacapital.net>,
        LKML <linux-kernel@vger.kernel.org>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>
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Hi Sebastian/Jonathan,

On Fri, Jan 28, 2022 at 9:35 AM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
> This report is due to CONFIG_PROVE_LOCKING=y _and_
> CONFIG_PROVE_RAW_LOCK_NESTING=y. It reports a nesting problem
> (raw_spinlock_t -> spinlock_t lock ordering) which becomes a real
> problem on PREEMPT_RT.

Hmm, I'm still having a tough time reproducing this. I'm trying to
understand your intuition. Is the problem you see that something else
in the IRQ path uses a raw_spinlock_t, and then with that lock still
held, we call invalidate_batched_entropy(), which takes an ordinary
spinlock_t, non-raw? And taking a spinlock-t while holding a
raw_spinlock_t is illegal?

Jason