linux-kernel - Re: [PATCH] serial: samsung: fix the inconsistency in spinlock

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Message-ID: <CANAwSgQuo_V_6J4C6MgdiDFeTTGaTPzoONSUKXwcanCpCWtZSg@mail.gmail.com>
Date:	Fri, 19 Feb 2016 00:44:53 +0530
From:	Anand Moon <linux.amoon@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: samsung: fix the inconsistency in spinlock

Hi Peter,

On 18 February 2016 at 23:18, Peter Hurley <peter@...leysoftware.com> wrote:
> Hi Anand,
>
> On 02/18/2016 09:40 AM, Anand Moon wrote:
>> From: Anand Moon <linux.amoon@...il.com>
>>
>> changes fix the correct order of the spin_lock_irqrestore/save.
>>
>> Signed-off-by: Anand Moon <linux.amoon@...il.com>
>> ---
>>  drivers/tty/serial/samsung.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
>> index d72cd73..96fe14d 100644
>> --- a/drivers/tty/serial/samsung.c
>> +++ b/drivers/tty/serial/samsung.c
>> @@ -759,9 +759,9 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
>>       }
>>
>>       if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
>> -             spin_unlock(&port->lock);
>> +             spin_unlock_irqrestore(&port->lock, flags);
>>               uart_write_wakeup(port);
>> -             spin_lock(&port->lock);
>> +             spin_lock_irqsave(&port->lock, flags);
>
> This driver shouldn't be dropping the spin lock at for write wakeup.
> If this is causing lock-ups in a line discipline, the line discipline
> needs fixed.
>

Thanks for pointing out.
Their is no lock up, just the inconstancy of the spin_lock.
Then I will resend this patch dropping the spin_unlock/spin_lock
around uart_write_wakeup.
Is that ok with you.

> Regards,
> Peter Hurley
>
>
>>       }
>>
>>       if (uart_circ_empty(xmit))
>>
>

Best Regards
-Anand Moon