From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH] cpuset: Replace all instances of time_t with time64_t Date: Wed, 25 Nov 2015 18:35:42 +0100 (CET) Message-ID: References: <2798266.9VZu01a7d1@wuerfel> Mime-Version: 1.0 Return-path: In-Reply-To: <2798266.9VZu01a7d1@wuerfel> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Arnd Bergmann Cc: Li Zefan , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Heena Sirwani , LKML , y2038-cunTk1MwBs8s++Sfvej+rw@public.gmane.org, John Stultz , Tejun Heo 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 > Reviewed-by: Arnd Bergmann > Signed-off-by: Arnd Bergmann > --- > 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 > #include > #include > +#include > #include > #include > > @@ -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; > >