linux-kernel - Re: [PATCH v6] ath9k: sleep for less time when unregistering hwrng

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Date:   Tue, 28 Jun 2022 12:55:57 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Gregory Erwin <gregerwin256@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kalle Valo <kvalo@...nel.org>,
        Rui Salvaterra <rsalvaterra@...il.com>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH v6] ath9k: sleep for less time when unregistering hwrng

Hi Herbert,

On Tue, Jun 28, 2022 at 12:52 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> On Tue, Jun 28, 2022 at 12:48:50PM +0200, Jason A. Donenfeld wrote:
> >
> > $ curl https://lore.kernel.org/lkml/20220627104955.534013-1-Jason@zx2c4.com/raw
> > | git am
> >
> > That one, if you want to give it a spin and see if that 5-6s is back
> > to ~1s or less.
>
> Whatever caused kthread_should_stop to return true should have
> woken the thread and caused schedule_timeout to return.
>
> If it's not waking the thread up then we should find out why.
>
> Oh wait you're checking kthread_should_stop before the schedule
> call instead of afterwards, that would do it.

Oh, that's a really good observation, thank you! I'll send a patch
that does it right. I have to check kthread_should_stop() before,
because the wake up might have been consumed by a sleep inside of the
hwrng ->read_data() function, causing it to return early. So we have
to check it before going to sleep again. And after, I need to be
checking the return value of schedule_timeout_interruptible(), which
I'm not in this latest. So v+1 coming up.

By the way, this thread might interest you:
https://lore.kernel.org/lkml/20220627145716.641185-1-Jason@zx2c4.com/

Jason