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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: Abhilash Jindal <klock.android@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Abhilash Jindal 2015-08-11 10:31:53 -04:00 committed by Greg Kroah-Hartman
parent 365741e6a6
commit d38c59e9ab
1 changed files with 5 additions and 5 deletions
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10
drivers/staging/comedi/drivers/serial2002.c
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@ -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);