[PATCH] cpuset: Replace all instances of time_t with time64_t

[PATCH] cpuset: Replace all instances of time_t with time64_t

[Arnd Bergmann]

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?

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;

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Re: [PATCH] cpuset: Replace all instances of time_t with time64_t

[Thomas Gleixner]

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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Reviewed-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
> Signed-off-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
> ---
> 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;
> 
> 

Re: [PATCH] cpuset: Replace all instances of time_t with time64_t

[Tejun Heo]

On Wed, Nov 25, 2015 at 04:16:55PM +0100, 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>

Applied to cgroup/for-4.5.

Thanks.

-- 
tejun
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Re: [PATCH] cpuset: Replace all instances of time_t with time64_t

[Zefan Li]

On 2015/11/26 3:01, Tejun Heo wrote:
> On Wed, Nov 25, 2015 at 04:16:55PM +0100, 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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Reviewed-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
>> Signed-off-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
>
> Applied to cgroup/for-4.5.
>

Acked