linux-kernel - Re: [RFC] With 8250 Designware UART, if writes to the LCR failed the kernel will hung up

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Date:	Wed, 11 Mar 2015 09:20:19 +0800
From:	Zhang Zhen <zhenzhang.zhang@...wei.com>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Tim Kryger <tim.kryger@...il.com>, Alan Cox <alan@...ux.intel.com>,
	"long.wanglong" <long.wanglong@...wei.com>,
	<linux-serial@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	<gregkh@...uxfoundation.org>, Jamie Iles <jamie@...ieiles.com>,
	Arnd Bergmann <arnd@...db.de>, <shenjiangjiang@...wei.com>,
	Wang Kai <morgan.wang@...wei.com>
Subject: Re: [RFC] With 8250 Designware UART, if writes to the LCR failed
 the kernel will hung up

On 2015/3/10 21:25, Peter Hurley wrote:
> On 03/09/2015 10:47 PM, Tim Kryger wrote:
>> The current workaround of clearing fifos and retrying a fixed number
>> of times isn't ideal but I'm not sure what else can be done given the
>> way this hardware works.
> 
> But hanging the machine is not an acceptable outcome.
> 
> Since the hang stems from the printk while already holding the port->lock,
> until I can fix the console write, I think it's best to comment out
> the dev_err() with a FIXME note.

Yeah，i agree.
> 
> The 8250 console write already checks port->sysrq to allow printk from
> within the driver so this solution just needs to be generalized.
> And there are debug uses of printk() from within the driver that are just
> as broken, so this isn't the only use case. (I want to do something
> similar for the au_serial-* i/o accessors too).
> 
> Regards,
> Peter Hurley
> 
> 
> 
> .
> 


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