On Wed, 25 Nov 2015, Arnd Bergmann wrote:

The following patch replaces all instances of time_t with time64_t i.e. change the type used for representing time from 32-bit to 64-bit. All 32-bit kernels to date use a signed 32-bit time_t type, which can only represent time until January 2038. Since embedded systems running 32-bit Linux are going to survive beyond that date, we have to change all current uses, in a backwards compatible way.

The patch also changes the function get_seconds() that returns a 32-bit integer to ktime_get_seconds() that returns seconds as 64-bit integer.

The patch changes the type of ticks from time_t to u32. We keep ticks as 32-bits as the function uses 32-bit arithmetic which would prove less expensive than 64-bit arithmetic and the function is expected to be called atleast once every 32 seconds.

Signed-off-by: Heena Sirwani heenasirwani@gmail.com Reviewed-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Arnd Bergmann arnd@arndb.de

---

This is an older patch I still had in my queue. Who should pick it up?

Tejun, Cc'ed

diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 10ae73611d80..c9ea63ff70a7 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -51,6 +51,7 @@ #include <linux/stat.h> #include <linux/string.h> #include <linux/time.h> +#include <linux/time64.h> #include <linux/backing-dev.h> #include <linux/sort.h> @@ -68,7 +69,7 @@ struct static_key cpusets_enabled_key __read_mostly = STATIC_KEY_INIT_FALSE; struct fmeter { int cnt; /* unprocessed events count */ int val; /* most recent output value */

• time_t time; /* clock (secs) when val computed */

• time64_t time; /* clock (secs) when val computed */ spinlock_t lock; /* guards read or write of above */

}; @@ -1374,7 +1375,7 @@ out: */ #define FM_COEF 933 /* coefficient for half-life of 10 secs */ -#define FM_MAXTICKS ((time_t)99) /* useless computing more ticks than this */ +#define FM_MAXTICKS ((u32)99) /* useless computing more ticks than this */ #define FM_MAXCNT 1000000 /* limit cnt to avoid overflow */ #define FM_SCALE 1000 /* faux fixed point scale */ @@ -1390,8 +1391,11 @@ static void fmeter_init(struct fmeter *fmp) /* Internal meter update - process cnt events and update value */ static void fmeter_update(struct fmeter *fmp) {

• time_t now = get_seconds();
• time_t ticks = now - fmp->time;

• time64_t now;
• u32 ticks;
• now = ktime_get_seconds();
• ticks = now - fmp->time;

if (ticks == 0) return;