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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Tue, 19 Jul 2022 22:05:31 +0200
Message-ID: <CAHmME9qrd25vfRYYvCWtPg+wVC5joEzzJiihCN+L4rqMfTL4Rg@mail.gmail.com>
Subject: Re: [PATCH v9] ath9k: let sleep be interrupted when unregistering hwrng
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>,
        Kalle Valo <kvalo@kernel.org>,
        Rui Salvaterra <rsalvaterra@gmail.com>,
        Valentin Schneider <vschneid@redhat.com>,
        stable <stable@vger.kernel.org>,
        Gregory Erwin <gregerwin256@gmail.com>,
        =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke@toke.dk>,
        Herbert Xu <herbert@gondor.apana.org.au>
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Hi Eric,

On Tue, Jul 19, 2022 at 9:26 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> "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.
>
> Is there any chance you can name the new function
> wake_up_task_interruptible instead of wake_up_process_interruptible.
>
> The name wake_up_process is wrong now, it does not wake up all threads
> of a process.  The name dates back to before linux supported multiple
> threads in a process, so it is grandfathered in until someone gets
> changes it.  But please let's not have a new function with a incorrect
> and confusing name.

No problem. v+1 incoming.

Jason