Commit d38c59e9 authored by Abhilash Jindal's avatar Abhilash Jindal Committed by Greg Kroah-Hartman
Browse files

staging: comedi: serial2002: Use monotonic clock 



Wall time obtained from do_gettimeofday is susceptible to sudden jumps due to
user setting the time or due to NTP.

Monotonic time is constantly increasing time better suited for comparing two
timestamps.

Signed-off-by: default avatarAbhilash Jindal <klock.android@gmail.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 365741e6

drivers/staging/comedi/drivers/serial2002.c

+5 −5
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ Status: in development 
#include <linux/delay.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/ktime.h>



#include <linux/termios.h>

#include <asm/ioctls.h>
@@ -121,9 +122,9 @@ static int serial2002_tty_write(struct file *f, unsigned char *buf, int count) 
static void serial2002_tty_read_poll_wait(struct file *f, int timeout)

{

	struct poll_wqueues table;

	struct timeval start, now;

	ktime_t start, now;



	do_gettimeofday(&start);

	start = ktime_get();

	poll_initwait(&table);

	while (1) {

		long elapsed;
@@ -134,9 +135,8 @@ static void serial2002_tty_read_poll_wait(struct file *f, int timeout) 
			    POLLHUP | POLLERR)) {

			break;

		}

		do_gettimeofday(&now);

		elapsed = 1000000 * (now.tv_sec - start.tv_sec) +

			  now.tv_usec - start.tv_usec;

		now = ktime_get();

		elapsed = ktime_us_delta(now, start);

		if (elapsed > timeout)

			break;

		set_current_state(TASK_INTERRUPTIBLE);