[OPW,kernel,v5,1/2] cpuset: Replace all instances of time_t with time64_t
diff mbox

Message ID 43cb8df7f4dec3c13c77aa38c8e6b15bc8b8da09.1413174804.git.heenasirwani@gmail.com
State New, archived
Headers show

Commit Message

Heena Sirwani Oct. 13, 2014, 4:51 a.m. UTC
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_real_ts64() that returns a struct of type timespec64
and use the tv_sec part which is 64-bit.

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>
---
 kernel/cpuset.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

Patch
diff mbox

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 52cb04c..c3e3aac 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 */
 };
 
@@ -1355,7 +1356,7 @@  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 */
 
@@ -1371,8 +1372,14 @@  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;
+	struct timespec64 timespec;
+	time64_t now;
+	u32 ticks;
+
+	/* One should probably use get_seconds64().*/
+	ktime_get_real_ts64(&timespec);		
+	now = timespec.tv_sec;
+	ticks = now - fmp->time;
 
 	if (ticks == 0)
 		return;