linux-kernel - Re: [PATCH 1/4] serial: 8250: omap: Fix freeing of resources on failed register

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Message-ID: <9ea78388-86f-736b-e46-b3bc6223ddbe@linux.intel.com>
Date:   Mon, 8 May 2023 12:55:38 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Tony Lindgren <tony@...mide.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Peter Hurley <peter@...leysoftware.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>, Johan Hovold <johan@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] serial: 8250: omap: Fix freeing of resources on
 failed register

On Mon, 8 May 2023, Tony Lindgren wrote:

> If serial8250_register_8250_port() fails, the SoC can hang as the
> deferred PMQoS work will still run as is not flushed and removed.
> 
> Fixes: 61929cf0169d ("tty: serial: Add 8250-core based omap driver")
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  drivers/tty/serial/8250/8250_omap.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -1532,7 +1532,9 @@ static int omap8250_probe(struct platform_device *pdev)
>  err:
>  	pm_runtime_dont_use_autosuspend(&pdev->dev);
>  	pm_runtime_put_sync(&pdev->dev);
> +	flush_work(&priv->qos_work);
>  	pm_runtime_disable(&pdev->dev);
> +	cpu_latency_qos_remove_request(&priv->pm_qos_request);
>  	return ret;

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

An unrelated comment to the patch itself, there seems to be somewhat 
handwavy and possibly wrong calculation for the pm qos latency. First of 
all, I think it would want something based on port->frame_time, and I'm 
far from convinced that 64 is right as it matches FIFO size which doesn't 
feel correct for a wakeup related time.

-- 
 i.