[PATCH v2] USB: usbmon: Remove timeval usage for timestamp

[PATCH v2] USB: usbmon: Remove timeval usage for timestamp

[Tina Ruchandani]

struct timeval' uses 32-bits for its seconds field and will overflow in
the year 2038 and beyond. This patch replaces the usage of 'struct timeval'
in mon_get_timestamp() with timespec64 which uses a 64-bit seconds field
and is y2038-safe. mon_get_timestamp() truncates the timestamp at 4096 seconds,
so the correctness of the code is not affected. This patch is part of a larger
attempt to remove instances of struct timeval and other 32-bit timekeeping
(time_t, struct timespec) from the kernel.

Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
---
Changes in v2:
- Switch to monotonic time since we only care about time elapsed.
---
 drivers/usb/mon/mon_text.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index ad40825..98e4f63 100644
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -9,6 +9,7 @@
 #include <linux/usb.h>
 #include <linux/slab.h>
 #include <linux/time.h>
+#include <linux/ktime.h>
 #include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/debugfs.h>
@@ -176,12 +177,12 @@ static inline char mon_text_get_data(struct mon_event_text *ep, struct urb *urb,
 
 static inline unsigned int mon_get_timestamp(void)
 {
-	struct timeval tval;
+	struct timespec64 now;
 	unsigned int stamp;
 
-	do_gettimeofday(&tval);
-	stamp = tval.tv_sec & 0xFFF;	/* 2^32 = 4294967296. Limit to 4096s. */
-	stamp = stamp * 1000000 + tval.tv_usec;
+	ktime_get_ts64(&now);
+	stamp = now.tv_sec & 0xFFF;  /* 2^32 = 4294967296. Limit to 4096s. */
+	stamp = stamp * USEC_PER_SEC + now.tv_nsec / NSEC_PER_USEC;
 	return stamp;
 }
 
-- 
2.6.0.rc2.230.g3dd15c0

Re: [PATCH v2] USB: usbmon: Remove timeval usage for timestamp

[Arnd Bergmann]

On Thursday 29 October 2015 22:58:28 Tina Ruchandani wrote:
> struct timeval' uses 32-bits for its seconds field and will overflow in
> the year 2038 and beyond. This patch replaces the usage of 'struct timeval'
> in mon_get_timestamp() with timespec64 which uses a 64-bit seconds field
> and is y2038-safe. mon_get_timestamp() truncates the timestamp at 4096 seconds,
> so the correctness of the code is not affected. This patch is part of a larger
> attempt to remove instances of struct timeval and other 32-bit timekeeping
> (time_t, struct timespec) from the kernel.
> 
> Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>