Messages in this thread | | | Date | Tue, 28 Oct 2014 16:43:42 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] timekeeping: Added a function to return tv_sec portion of ktime_get_real_ts64() |
| |
On Mon, 27 Oct 2014, Heena Sirwani wrote: > The following patch adds a function to return tv_sec portion of > ktime_get_real_ts64() function in order to have a function that returns > seconds as 64-bit integers instead of 32-bit integers to address the > y2038 problem. > > The function is similar to get_seconds() function except that it > includes read_seqcount_retry loop which is required for 32-bit > architectures. This is because 32-bit machines cannot access 64-bit > tk->xtime_sec variable atomically, requiring two 32-bit register loads. > > Signed-off-by: Heena Sirwani <heenasirwani@gmail.com> > Reviewed-by: Arnd Bergmann <arnd@arndb.de> > --- > Changes in v2: > - Removed the local variable nsecs as it was not required. > > include/linux/timekeeping.h | 1 + > kernel/time/timekeeping.c | 19 +++++++++++++++++++ > 2 files changed, 20 insertions(+) > > diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h > index 115d55e..91454de 100644 > --- a/include/linux/timekeeping.h > +++ b/include/linux/timekeeping.h > @@ -29,6 +29,7 @@ struct timespec get_monotonic_coarse(void); > extern void getrawmonotonic(struct timespec *ts); > extern void ktime_get_ts64(struct timespec64 *ts); > extern time64_t ktime_get_seconds(void); > +extern time64_t ktime_get_real_seconds(void); > > extern int __getnstimeofday64(struct timespec64 *tv); > extern void getnstimeofday64(struct timespec64 *tv); > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 93fc596..c17c620 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -673,6 +673,25 @@ time64_t ktime_get_seconds(void) > } > EXPORT_SYMBOL_GPL(ktime_get_seconds); > > +time64_t ktime_get_real_seconds(void) > +{ > + time64_t seconds; > + struct timekeeper *tk = &tk_core.timekeeper; > + unsigned int seq; > + > + if (IS_ENABLED(CONFIG_64BIT)) > + return tk->xtime_sec; > + > + do { > + seq = read_seqcount_begin(&tk_core.seq); > + seconds = tk->xtime_sec; > + > + } while (read_seqcount_retry(&tk_core.seq, seq)); > + > + return seconds; > +} > +EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
Nice and clean implementation! Though I wonder whether we should just name it get_seconds64().
Thanks,
tglx
| |