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From: "tiantao (H)" <tiantao6@huawei.com>
To: Johan Hovold <johan@kernel.org>, Tian Tao <tiantao6@hisilicon.com>
Cc: <gregkh@linuxfoundation.org>, <jirislaby@kernel.org>,
	<afaerber@suse.de>, <manivannan.sadhasivam@linaro.org>,
	<linux-serial@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tty: serial: replace spin_lock_irqsave by spin_lock in hard IRQ
Date: Fri, 20 Nov 2020 19:25:03 +0800	[thread overview]
Message-ID: <9ce93d7b-f769-58ed-e6bf-95c34bd0123e@huawei.com> (raw)
In-Reply-To: <X7d85DKvisjA3nYv@localhost>



在 2020/11/20 16:23, Johan Hovold 写道:
> On Thu, Nov 19, 2020 at 05:01:29PM +0800, Tian Tao wrote:
>> The code has been in a irq-disabled context since it is hard IRQ. There
>> is no necessity to do it again.
>>
>> Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
>> ---
>>   drivers/tty/serial/owl-uart.c | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
>> index c149f8c3..472fdaf 100644
>> --- a/drivers/tty/serial/owl-uart.c
>> +++ b/drivers/tty/serial/owl-uart.c
>> @@ -251,10 +251,9 @@ static void owl_uart_receive_chars(struct uart_port *port)
>>   static irqreturn_t owl_uart_irq(int irq, void *dev_id)
>>   {
>>   	struct uart_port *port = dev_id;
>> -	unsigned long flags;
>>   	u32 stat;
>>   
>> -	spin_lock_irqsave(&port->lock, flags);
>> +	spin_lock(&port->lock);
> 
> Same thing here; this will break with forced irq threading (i.e.
> "threadirqs") since the console code can still end up being called from
> interrupt context.
As the following code shows, owl_uart_irq does not run in the irq 
threading context.
  ret = request_irq(port->irq, owl_uart_irq, IRQF_TRIGGER_HIGH,
                         "owl-uart", port);
         if (ret)
                 return ret;

> 
>>   	stat = owl_uart_read(port, OWL_UART_STAT);
>>   
>> @@ -268,7 +267,7 @@ static irqreturn_t owl_uart_irq(int irq, void *dev_id)
>>   	stat |= OWL_UART_STAT_RIP | OWL_UART_STAT_TIP;
>>   	owl_uart_write(port, stat, OWL_UART_STAT);
>>   
>> -	spin_unlock_irqrestore(&port->lock, flags);
>> +	spin_unlock(&port->lock);
>>   
>>   	return IRQ_HANDLED;
>>   }
> 
> Johan
> 
> .
> 


  reply	other threads:[~2020-11-20 11:25 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-19  9:01 Tian Tao
2020-11-19  9:03 ` Jiri Slaby
2020-11-20  8:23 ` Johan Hovold
2020-11-20 11:25   ` tiantao (H) [this message]
2020-11-20 12:49     ` Johan Hovold
2020-11-20 20:00       ` David Laight
2020-11-21 15:17         ` Johan Hovold

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