Re: [PATCH] tty: serial: replace spin_lock_irqsave by spin_lock in hard IRQ

[tiantao (H)]

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@xxxxxxxxxxxxx>
> > ---
> >   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
>
> .