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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 26 Jun 2023 10:24:55 -0700
Message-ID: <CAKwvOdnTzcG0DY9SScu1JuV4Q0Ka60qm9jdK2TjA1Cav8En-mQ@mail.gmail.com>
Subject: Re: Thread-safety annotations for irq/rcu/atomic contexts
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Lukas Bulwahn <lukas.bulwahn@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Marco Elver <elver@google.com>,
        clang-built-linux <llvm@lists.linux.dev>
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(minus old ML, plus new ML)

On Mon, Jun 26, 2023 at 10:21=E2=80=AFAM 'Dmitry Vyukov' via Clang Built Li=
nux
<clang-built-linux@googlegroups.com> wrote:
>
> Hi,
>
> Previous Lukas' attempt to apply clang thread-safety annotations to the k=
ernel:
> https://clangbuiltlinux.github.io/CBL-meetup-2020-slides/lukas/tsa.pdf
>
> I am thinking if the annotations can be used to check for functions
> that must/must not be called from irq/atomic/rcu_read/etc contexts.
> Namely, we create global fake locks that denote these contexts, then
> annotate spin_lock_irqsave/irqrestore/etc as taking releasing these
> locks, and finally annotate functions are requiring/excluding these
> contexts:
>
> void foo() require(irq_context);
> void bar() exclude(irq_context);
> void baz() require(rcu_read_context);
>
> This may help to catch "suspicious RCU usage", "scheduling while
> atomic" and similar bug types statically. I suspect it may also be
> simpler (?) to do rather than annotating all normal locks.
>
> Does it make any sense?
>
> --
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--=20
Thanks,
~Nick Desaulniers