linux-kernel - Re: [PATCH v1] ASoC: meson: axg-fifo: set option to use raw spinlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240806065740.DAZwSnQ7@linutronix.de>
Date: Tue, 6 Aug 2024 08:57:40 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Mark Brown <broonie@...nel.org>
Cc: Jerome Brunet <jbrunet@...libre.com>, linux-rt-users@...r.kernel.org,
	Arseniy Krasnov <avkrasnov@...utedevices.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Kevin Hilman <khilman@...libre.com>,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
	alsa-devel@...a-project.org, linux-sound@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...rdevices.ru, oxffffaa@...il.com,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v1] ASoC: meson: axg-fifo: set option to use raw spinlock

On 2024-08-05 17:56:22 [+0100], Mark Brown wrote:
> On Mon, Aug 05, 2024 at 05:33:09PM +0200, Sebastian Andrzej Siewior wrote:
> 
> > I'm not sure if making the lock a raw_spinlock_t solves all the
> > problems. The regmap is regmap_mmio so direct memory-access and looks
> > simple enough to do so. In regmap_mmio_write() I see clk_enable() and
> > and this uses a spinlock_t so we should be back at the same problem.
> 
> The clk_enable() is optional, users simply shouldn't use the internal
> clock management with devices that it'll cause problems for.
> 
> > There might be an additional problem if reg-caching is enabled.
> 
> The flat cache is there mostly for the benefit of things accessed from
> interrupt context, it guarantees to never do any allocations and doesn't
> lock.  You can also use other caches if you ensure that any registers
> accessed in interrupt context are already cached so won't trigger any
> new allocations.

My point is simply that those two things could complicate things further
if the desired fix is to (always) use raw_spinlock_t.

Sebastian