* [PATCH v5 0/2] cpuset: Replace instances of time_t with time64_t to solve y2038 problem
@ 2014-10-13 4:49 Heena Sirwani
[not found] ` <cover.1413174804.git.heenasirwani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Heena Sirwani @ 2014-10-13 4:49 UTC (permalink / raw)
To: opw-kernel-/JYPxA39Uh5TLH3MbocFFw
Cc: arnd-r2nGTMty4D4, lizefan-hv44wF8Li93QT0dZR+AlfA,
cgroups-u79uwXL29TY76Z2rM5mHXA
The following patchset replaces instances of time_t with time64_t to
address the y2038 problem. The patchset also makes the code independent
of settimeofday().
Changes in v2:
- Changed the function get_seconds() that return 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.
- Change 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.
Changes in v3:
- Changed commenting style.
Changes in v4:
- Changed the subject tag.
Changes in v5:
- Changed a comment and added a patch that make the code
independent of settimeofday().
Heena Sirwani (2):
cpuset: Replace all instances of time_t with time64_t
cpuset: Replace ktime_get_real_ts64() with ktime_get_ts64()
kernel/cpuset.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
--
1.9.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH v5 1/2] cpuset: Replace all instances of time_t with time64_t
[not found] ` <cover.1413174804.git.heenasirwani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
@ 2014-10-13 4:51 ` Heena Sirwani
2014-10-13 4:52 ` [PATCH v5 2/2] cpuset: Replace ktime_get_real_ts64() with ktime_get_ts64() Heena Sirwani
1 sibling, 0 replies; 3+ messages in thread
From: Heena Sirwani @ 2014-10-13 4:51 UTC (permalink / raw)
To: opw-kernel-/JYPxA39Uh5TLH3MbocFFw
Cc: arnd-r2nGTMty4D4, lizefan-hv44wF8Li93QT0dZR+AlfA,
cgroups-u79uwXL29TY76Z2rM5mHXA
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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
kernel/cpuset.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
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(×pec);
+ now = timespec.tv_sec;
+ ticks = now - fmp->time;
if (ticks == 0)
return;
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH v5 2/2] cpuset: Replace ktime_get_real_ts64() with ktime_get_ts64()
[not found] ` <cover.1413174804.git.heenasirwani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-10-13 4:51 ` [PATCH v5 1/2] cpuset: Replace all instances of time_t with time64_t Heena Sirwani
@ 2014-10-13 4:52 ` Heena Sirwani
1 sibling, 0 replies; 3+ messages in thread
From: Heena Sirwani @ 2014-10-13 4:52 UTC (permalink / raw)
To: opw-kernel-/JYPxA39Uh5TLH3MbocFFw
Cc: arnd-r2nGTMty4D4, lizefan-hv44wF8Li93QT0dZR+AlfA,
cgroups-u79uwXL29TY76Z2rM5mHXA
The following patch makes the kernel code independent of the
setimeofday() function by replacing the function ktime_get_real_ts64()
with ktime_get_ts64().
The function calculates the interval between two successive calls to
fmeter_update() and between these if a call to settimeofday() is called
it would lead to erroneous calculation of the interval. The function
ktime_get_ts64() is the monotonic wall-time clock that does an extra
calculation to remove the effects of settimeofday().
Signed-off-by: Heena Sirwani <heenasirwani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
kernel/cpuset.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c3e3aac..98cf976 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1377,7 +1377,7 @@ static void fmeter_update(struct fmeter *fmp)
u32 ticks;
/* One should probably use get_seconds64().*/
- ktime_get_real_ts64(×pec);
+ ktime_get_ts64(×pec);
now = timespec.tv_sec;
ticks = now - fmp->time;
--
1.9.1
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2014-10-13 4:49 [PATCH v5 0/2] cpuset: Replace instances of time_t with time64_t to solve y2038 problem Heena Sirwani
[not found] ` <cover.1413174804.git.heenasirwani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-10-13 4:51 ` [PATCH v5 1/2] cpuset: Replace all instances of time_t with time64_t Heena Sirwani
2014-10-13 4:52 ` [PATCH v5 2/2] cpuset: Replace ktime_get_real_ts64() with ktime_get_ts64() Heena Sirwani
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