cpuset: Replace all instances of time_t with time64_t (d2b43658) · Commits · 戴 / test

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:

Tejun Heo <tj@kernel.org>

kernel/cpuset.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -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;

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