linux-kernel - Re: ath11k: checking RCU usage

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Date: Mon, 22 Jan 2024 14:10:16 +0100
From: Johan Hovold <johan@...nel.org>
To: Kalle Valo <kvalo@...nel.org>
Cc: Johan Hovold <johan+linaro@...nel.org>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	ath11k@...ts.infradead.org, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: ath11k: checking RCU usage

Hi Kalle,

On Sat, Jan 13, 2024 at 12:26:53PM +0200, Kalle Valo wrote:
> (old discussion, changing title)
> 
> Johan Hovold <johan@...nel.org> writes:
> 
> > On Tue, Oct 24, 2023 at 05:07:38PM +0300, Kalle Valo wrote:

> >> Thanks for the fixes. I really like using lockdep_assert_held() to
> >> document if a function requires some lock held, is there anything
> >> similar for RCU?
> >
> > Not really, but the checking is instead built into the primitives like
> > rcu_dereference() and enabled whenever CONFIG_PROVE_RCU is set.
> >
> > For some special cases, we have open-coded checks like:
> >
> > 	RCU_LOCKDEP_WARN(!rcu_read_lock_held());
> >
> > which similarly depend on CONFIG_PROVE_RCU or simply
> >
> > 	WARN_ON_ONCE(!rcu_read_lock_held());
> 
> I just found out that sparse has __must_hold():
> 
> https://lore.kernel.org/linux-wireless/87sf31hhfp.fsf@kernel.org/
> 
> That looks promising, should we start using that in ath11k and ath12k to
> check our RCU usage?

I see that Johannes already commented on this in the thread above.

I'm pretty sure smatch can't be used for this.

Johan