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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org
Cc:     Gregory Erwin <gregerwin256@gmail.com>,
        Kalle Valo <kvalo@kernel.org>,
        Rui Salvaterra <rsalvaterra@gmail.com>, stable@vger.kernel.org
Subject: Re: [PATCH v8] ath9k: let sleep be interrupted when unregistering
 hwrng
In-Reply-To: <20220629114240.946411-1-Jason@zx2c4.com>
References: <Yrw5f8GN2fh2orid@zx2c4.com>
 <20220629114240.946411-1-Jason@zx2c4.com>
Date:   Tue, 05 Jul 2022 00:04:46 +0200
Message-ID: <874jzw8rgh.fsf@toke.dk>
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"Jason A. Donenfeld" <Jason@zx2c4.com> writes:

> There are two deadlock scenarios that need addressing, which cause
> problems when the computer goes to sleep, the interface is set down, and
> hwrng_unregister() is called. When the deadlock is hit, sleep is delayed
> for tens of seconds, causing it to fail. These scenarios are:
>
> 1) The hwrng kthread can't be stopped while it's sleeping, because it
>    uses msleep_interruptible() instead of schedule_timeout_interruptible(=
).
>    The fix is a simple moving to the correct function. At the same time,
>    we should cleanup a common and useless dmesg splat in the same area.
>
> 2) A normal user thread can't be interrupted by hwrng_unregister() while
>    it's sleeping, because hwrng_unregister() is called from elsewhere.
>    The solution here is to keep track of which thread is currently
>    reading, and asleep, and signal that thread when it's time to
>    unregister. There's a bit of book keeping required to prevent
>    lifetime issues on current.
>
> Reported-by: Gregory Erwin <gregerwin256@gmail.com>
> Cc: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>
> Cc: Kalle Valo <kvalo@kernel.org>
> Cc: Rui Salvaterra <rsalvaterra@gmail.com>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: stable@vger.kernel.org
> Fixes: fcd09c90c3c5 ("ath9k: use hw_random API instead of directly dumpin=
g into random.c")
> Link: https://lore.kernel.org/all/CAO+Okf6ZJC5-nTE_EJUGQtd8JiCkiEHytGgDsF=
GTEjs0c00giw@mail.gmail.com/
> Link: https://lore.kernel.org/lkml/CAO+Okf5k+C+SE6pMVfPf-d8MfVPVq4PO7EY8H=
ys_DVXtent3HA@mail.gmail.com/
> Link: https://bugs.archlinux.org/task/75138
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

With the change to EXPORT_SYMBOL_GPL() for wake_up_state that Kalle has
kindly agreed to fix up while applying:

Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk>