[PATCH 1/1] serial/uuc_uart: Set shutdown timeout to CONFIG_HZ independent 2ms

[PATCH 1/1] serial/uuc_uart: Set shutdown timeout to CONFIG_HZ independent 2ms

[Alexander Stein]

schedule_timeout takes a timeout in jiffies resolution. So pass 2ms
as a converted jiffies value. This makes the timeout independent of
CONFIG_HZ.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
---
 drivers/tty/serial/ucc_uart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/ucc_uart.c b/drivers/tty/serial/ucc_uart.c
index 481eb29..c6c01a4 100644
--- a/drivers/tty/serial/ucc_uart.c
+++ b/drivers/tty/serial/ucc_uart.c
@@ -827,7 +827,7 @@ static void qe_uart_shutdown(struct uart_port *port)
 			break;
 		}
 		set_current_state(TASK_UNINTERRUPTIBLE);
-		schedule_timeout(2);
+		schedule_timeout(msecs_to_jiffies(2));
 	}
 
 	if (qe_port->wait_closing) {
-- 
2.7.3

Re: [PATCH 1/1] serial/uuc_uart: Set shutdown timeout to CONFIG_HZ independent 2ms

[Timur Tabi]

Alexander Stein wrote:
> -		schedule_timeout(2);
> +		schedule_timeout(msecs_to_jiffies(2));

NACK.

So I don't remember why I wrote this code, but I don't think I was 
expecting it to be 2ms.  Instead, I think I just wanted it to be some 
delay, but I believed that schedule_timeout(1) was too short or would be 
"optimized" out somehow.

Note that right below this, I do:

	if (qe_port->wait_closing) {
		/* Wait a bit longer */
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(qe_port->wait_closing);
	}

And wait_closing is a number of jiffies, so I knew that 
schedule_timeout() took jiffies as a parameter.

So I think I'm going to NACK this patch, since I believe I knew what I 
was doing when I wrote it five years ago.

Re: [PATCH 1/1] serial/uuc_uart: Set shutdown timeout to CONFIG_HZ independent 2ms

[Alexander Stein]

On Monday 05 December 2016 10:04:27, Timur Tabi wrote:
> Alexander Stein wrote:
> > -		schedule_timeout(2);
> > +		schedule_timeout(msecs_to_jiffies(2));
> 
> NACK.
> 
> So I don't remember why I wrote this code, but I don't think I was
> expecting it to be 2ms.  Instead, I think I just wanted it to be some
> delay, but I believed that schedule_timeout(1) was too short or would be
> "optimized" out somehow.
> 
> Note that right below this, I do:
> 
> 	if (qe_port->wait_closing) {
> 		/* Wait a bit longer */
> 		set_current_state(TASK_UNINTERRUPTIBLE);
> 		schedule_timeout(qe_port->wait_closing);
> 	}
> 
> And wait_closing is a number of jiffies, so I knew that
> schedule_timeout() took jiffies as a parameter.
> 
> So I think I'm going to NACK this patch, since I believe I knew what I
> was doing when I wrote it five years ago.

Okay, I was just wondering why the timeout is dependant on the timer tick. 
That didn't seem obvious to me.
Rethinking about this, I would rather replace those lines with msleep instead.

Best regards,
Alexander

Re: [PATCH 1/1] serial/uuc_uart: Set shutdown timeout to CONFIG_HZ independent 2ms

[Timur Tabi]

Alexander Stein wrote:
> Okay, I was just wondering why the timeout is dependant on the timer tick.
> That didn't seem obvious to me.
> Rethinking about this, I would rather replace those lines with msleep instead.

What's wrong with leaving it as-is?  The code is five years old, and 
Freescale/NXP barely uses the QE any more.  I don't have access to any 
hardware to test any changes you would propose.