linux-kernel - Re: [PATCH v2] serial: sifive: lock port in startup()/shutdown() callbacks

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Message-ID: <Z_erp2nLRKzLXuwF@pathway.suse.cz>
Date: Thu, 10 Apr 2025 13:29:43 +0200
From: Petr Mladek <pmladek@...e.com>
To: Ryo Takakura <ryotkkr98@...il.com>
Cc: alex@...ti.fr, aou@...s.berkeley.edu, bigeasy@...utronix.de,
	conor.dooley@...rochip.com, gregkh@...uxfoundation.org,
	jirislaby@...nel.org, john.ogness@...utronix.de, palmer@...belt.com,
	paul.walmsley@...ive.com, samuel.holland@...ive.com,
	u.kleine-koenig@...libre.com, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-serial@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] serial: sifive: lock port in startup()/shutdown()
 callbacks

On Sat 2025-04-05 23:53:54, Ryo Takakura wrote:
> startup()/shutdown() callbacks access SIFIVE_SERIAL_IE_OFFS.
> The register is also accessed from write() callback.
> 
> If console were printing and startup()/shutdown() callback
> gets called, its access to the register could be overwritten.
> 
> Add port->lock to startup()/shutdown() callbacks to make sure
> their access to SIFIVE_SERIAL_IE_OFFS is synchronized against
> write() callback.
> 
> Fixes: 45c054d0815b ("tty: serial: add driver for the SiFive UART")
> Signed-off-by: Ryo Takakura <ryotkkr98@...il.com>
> Cc: stable@...r.kernel.org

I do not have the hardware around so I could not test it.
But the change make sense. It fixes a real race.
And the code looks reasonable:

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr