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Message-ID: <20150527012212.GA2613@tinar>
Date: Wed, 27 May 2015 06:52:12 +0530
From: Tina Ruchandani <ruchandani.tina@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Karsten Keil <isdn@...ux-pingi.de>, netdev@...r.kernel.org,
y2038@...ts.linaro.org
Subject: [PATCH v3] isdn: Use ktime_t instead of 'struct timeval'
'struct timeval' uses 32-bit representation for seconds which will
overflow in year 2038 and beyond. mISDN/clock.c needs to compute and
store elapsed time in intervals of 125 microseconds. This patch replaces
the usage of 'struct timeval' with 64-bit ktime_t which is y2038 safe.
The patch also replaces do_gettimeofday() (wall-clock time) with
ktime_get() (monotonic time) since we only care about elapsed time here.
Signed-off-by: Tina Ruchandani <ruchandani.tina@...il.com>
Suggested-by: Arnd Bergmnann <arnd@...db.de>
--
Changes in v3:
- Use division scheme suggested by Arnd Bergmann to avoid
a (64-bit variable) / (32-bit variable) expression.
Changes in v2:
- Avoid possible truncation bug caused by assigning ktime_us_delta
output to a 16-bit number.
- Use ktime_us_delta, more concise than a combination of ktime_sub
and ktime_to_us.
---
drivers/isdn/mISDN/clock.c | 56 ++++++++++++++++++----------------------------
include/linux/mISDNif.h | 2 +-
2 files changed, 23 insertions(+), 35 deletions(-)
diff --git a/drivers/isdn/mISDN/clock.c b/drivers/isdn/mISDN/clock.c
index 693fb7c..0ea7e2f 100644
--- a/drivers/isdn/mISDN/clock.c
+++ b/drivers/isdn/mISDN/clock.c
@@ -37,6 +37,7 @@
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/spinlock.h>
+#include <linux/ktime.h>
#include <linux/mISDNif.h>
#include <linux/export.h>
#include "core.h"
@@ -45,7 +46,7 @@ static u_int *debug;
static LIST_HEAD(iclock_list);
static DEFINE_RWLOCK(iclock_lock);
static u16 iclock_count; /* counter of last clock */
-static struct timeval iclock_tv; /* time stamp of last clock */
+static ktime_t iclock_tv; /* time stamp of last clock */
static int iclock_tv_valid; /* already received one timestamp */
static struct mISDNclock *iclock_current;
@@ -53,7 +54,7 @@ void
mISDN_init_clock(u_int *dp)
{
debug = dp;
- do_gettimeofday(&iclock_tv);
+ iclock_tv = ktime_get();
}
static void
@@ -139,12 +140,11 @@ mISDN_unregister_clock(struct mISDNclock *iclock)
EXPORT_SYMBOL(mISDN_unregister_clock);
void
-mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
+mISDN_clock_update(struct mISDNclock *iclock, int samples, ktime_t *tv)
{
u_long flags;
- struct timeval tv_now;
- time_t elapsed_sec;
- int elapsed_8000th;
+ ktime_t tv_now;
+ u16 delta;
write_lock_irqsave(&iclock_lock, flags);
if (iclock_current != iclock) {
@@ -160,28 +160,22 @@ mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
/* increment sample counter by given samples */
iclock_count += samples;
if (tv) { /* tv must be set, if function call is delayed */
- iclock_tv.tv_sec = tv->tv_sec;
- iclock_tv.tv_usec = tv->tv_usec;
- } else
- do_gettimeofday(&iclock_tv);
+ iclock_tv = *tv;
+ } else {
+ iclock_tv = ktime_get();
+ }
} else {
/* calc elapsed time by system clock */
if (tv) { /* tv must be set, if function call is delayed */
- tv_now.tv_sec = tv->tv_sec;
- tv_now.tv_usec = tv->tv_usec;
- } else
- do_gettimeofday(&tv_now);
- elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
- elapsed_8000th = (tv_now.tv_usec / 125)
- - (iclock_tv.tv_usec / 125);
- if (elapsed_8000th < 0) {
- elapsed_sec -= 1;
- elapsed_8000th += 8000;
+ tv_now = *tv;
+ } else {
+ tv_now = ktime_get();
}
+ delta = ktime_divns(ktime_sub(tv_now, iclock_tv),
+ (NS_PER_SEC / 8000));
/* add elapsed time to counter and set new timestamp */
- iclock_count += elapsed_sec * 8000 + elapsed_8000th;
- iclock_tv.tv_sec = tv_now.tv_sec;
- iclock_tv.tv_usec = tv_now.tv_usec;
+ iclock_count += delta;
+ iclock_tv = tv_now;
iclock_tv_valid = 1;
if (*debug & DEBUG_CLOCK)
printk("Received first clock from source '%s'.\n",
@@ -195,22 +189,16 @@ unsigned short
mISDN_clock_get(void)
{
u_long flags;
- struct timeval tv_now;
- time_t elapsed_sec;
- int elapsed_8000th;
+ ktime_t tv_now;
+ u16 delta;
u16 count;
read_lock_irqsave(&iclock_lock, flags);
/* calc elapsed time by system clock */
- do_gettimeofday(&tv_now);
- elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
- elapsed_8000th = (tv_now.tv_usec / 125) - (iclock_tv.tv_usec / 125);
- if (elapsed_8000th < 0) {
- elapsed_sec -= 1;
- elapsed_8000th += 8000;
- }
+ tv_now = ktime_get();
+ delta = ktime_divns(ktime_sub(tv_now, iclock_tv), (NS_PER_SEC / 8000));
/* add elapsed time to counter */
- count = iclock_count + elapsed_sec * 8000 + elapsed_8000th;
+ count = iclock_count + delta;
read_unlock_irqrestore(&iclock_lock, flags);
return count;
}
diff --git a/include/linux/mISDNif.h b/include/linux/mISDNif.h
index 246a352..ac02c54 100644
--- a/include/linux/mISDNif.h
+++ b/include/linux/mISDNif.h
@@ -596,7 +596,7 @@ static inline struct mISDNdevice *dev_to_mISDN(struct device *dev)
}
extern void set_channel_address(struct mISDNchannel *, u_int, u_int);
-extern void mISDN_clock_update(struct mISDNclock *, int, struct timeval *);
+extern void mISDN_clock_update(struct mISDNclock *, int, ktime_t *);
extern unsigned short mISDN_clock_get(void);
extern const char *mISDNDevName4ch(struct mISDNchannel *);
--
2.2.0.rc0.207.ga3a616c
--
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