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References: <20210914192515.9273-1-linus.luessing@c0d3.blue>
 <20210914192515.9273-4-linus.luessing@c0d3.blue>
From:   Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH 3/3] ath9k: Fix potential hw interrupt resume during reset
Message-ID: <255a49c7-d763-50d9-87e0-da22f4a9b053@nbd.name>
Date:   Wed, 15 Sep 2021 11:48:55 +0200
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On 2021-09-14 21:25, Linus Lüssing wrote:
> From: Linus Lüssing <ll@simonwunderlich.de>
> 
> There is a small risk of the ath9k hw interrupts being reenabled in the
> following way:
> 
> 1) ath_reset_internal()
>    ...
>    -> disable_irq()
>       ...
>       <- returns
> 
>                       2) ath9k_tasklet()
>                          ...
>                          -> ath9k_hw_resume_interrupts()
>                          ...
> 
> 1) ath_reset_internal() continued:
>    -> tasklet_disable(&sc->intr_tq); (= ath9k_tasklet() off)
> 
> By first disabling the ath9k interrupt there is a small window
> afterwards which allows ath9k hw interrupts being reenabled through
> the ath9k_tasklet() before we disable this tasklet in
> ath_reset_internal(). Leading to having the ath9k hw interrupts enabled
> during the reset, which we should avoid.
I don't see a way in which interrupts can be re-enabled through the
tasklet. disable_irq disables the entire PCI IRQ (not through ath9k hw
registers), and they will only be re-enabled by the corresponding
enable_irq call.

- Felix