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Date: Mon, 10 Aug 2026 11:24:41 +0100
From: Daniel Thompson <danielt@kernel.org>
To: Guangshuo Li <lgs201920130244@gmail.com>
Cc: Olivia Mackall <olivia@selenic.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Linus Walleij <linusw@kernel.org>, linux-crypto@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] hwrng: stm32: fix usage_count leak when
 autosuspend_delay is negative
Message-ID: <anmm6X4MLpyIH8K1@aspen.lan>
References: <20260808074510.2655473-1-lgs201920130244@gmail.com>
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In-Reply-To: <20260808074510.2655473-1-lgs201920130244@gmail.com>

On Sat, Aug 08, 2026 at 03:45:10PM +0800, Guangshuo Li wrote:
> stm32_rng_probe() calls pm_runtime_use_autosuspend(), but neither the
> probe failure path nor stm32_rng_remove() calls the matching
> pm_runtime_dont_use_autosuspend() before disabling runtime PM.
>
> If the autosuspend delay is set to a negative value while autosuspend
> is enabled, the runtime PM core increments usage_count to prevent
> runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
> during teardown, this reference is not dropped and usage_count remains
> unbalanced.

If calls to pm_runtime_use_autosuspend() must be paired with
pm_runtime_dont_use_autosuspend() then I wonder if having a
devm_pm_runtime_use_autosuspend() would be worthwhile?

That way stm32_rng_remove() could be entirely replaced with devres
cleanup.


Daniel.