Re: Re: [PATCH 1/2] Add function to convert between calendar time and broken-down time for universal use
- From: Zhaolei <zhaolei@xxxxxxxxxxxxxx>
- Date: Wed, 15 Jul 2009 08:59:53 +0800
Andrew Morton wrote:
On Tue, 14 Jul 2009 16:03:12 +0800
Zhaolei <zhaolei@xxxxxxxxxxxxxx> wrote:
There are many similar code in kernel for one object:
convert time between calendar time and broken-down time.
Here is some source I found:
fs/ncpfs/dir.c
fs/smbfs/proc.c
fs/fat/misc.c
fs/udf/udftime.c
fs/cifs/netmisc.c
net/netfilter/xt_time.c
drivers/scsi/ips.c
drivers/input/misc/hp_sdc_rtc.c
drivers/rtc/rtc-lib.c
arch/ia64/hp/sim/boot/fw-emu.c
arch/m68k/mac/misc.c
arch/powerpc/kernel/time.c
arch/parisc/include/asm/rtc.h
...
We can make a common function for this type of conversion,
At least we can get following benefit:
1: Make kernel simple and unify
2: Easy to fix bug in converting code
3: Reduce clone of code in future
For example, I'm trying to make ftrace display walltime,
this patch will make me easy.
The objective is a good one. Have you verified that these new library
functions can be used by most/all of the above callers?
Hello, Andrew
Thanks for your review.
I checked some of them, and I think this new library can make them simple.
A example is my patch for fs/fat/misc.c.
Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
---
include/linux/time.h | 9 +++
kernel/time/Makefile | 2 +-
kernel/time/timeconv.c | 180 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 190 insertions(+), 1 deletions(-)
create mode 100644 kernel/time/timeconv.c
diff --git a/include/linux/time.h b/include/linux/time.h
index ea16c1a..0ae0e6e 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -151,6 +151,15 @@ extern void update_xtime_cache(u64 nsec);
struct tms;
extern void do_sys_times(struct tms *);
+extern void gmtime(__kernel_time_t totalsecs,
+ unsigned int *year, unsigned int *mon, unsigned int *mday,
+ unsigned int *hour, unsigned int *min, unsigned int *sec,
+ unsigned int *wday, unsigned int *yday);
+extern void localtime(__kernel_time_t totalsecs,
+ unsigned int *year, unsigned int *mon, unsigned int *mday,
+ unsigned int *hour, unsigned int *min, unsigned int *sec,
+ unsigned int *wday, unsigned int *yday);
I'd imagine that many callers would at least need some types changed -
replace `int' with `unsigned int', etc. Not a big problem.
Actually, I considered to use int instead, but at last I use unsigned int to
make it same with mktime() which is already in kernel.
/**
* timespec_to_ns - Convert timespec to nanoseconds
* @ts: pointer to the timespec variable to be converted
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 0b0a636..ee26662 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -1,4 +1,4 @@
-obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o
+obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o timeconv.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
diff --git a/kernel/time/timeconv.c b/kernel/time/timeconv.c
new file mode 100644
index 0000000..c710605
--- /dev/null
+++ b/kernel/time/timeconv.c
@@ -0,0 +1,180 @@
+/*
+ * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
The patch is significantly wordwrapped by your email client.
The patch has no tabs in it at all - either some serious cleanup is
needed of your email client is performing tab-to-space conversion.
Sorry...I reinstalled a email client......
I'll fix it and resend this patch.
+ * This file is part of the GNU C Library.
+ * Contributed by Paul Eggert (eggert@xxxxxxxxxxx).
+ *
+ * The GNU C Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The GNU C Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with the GNU C Library; see the file COPYING.LIB. If not,
+ * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/*
+ * Converts the calendar time to broken-down time representation
+ * Based on code from glibc-2.6
+ *
+ * 2009-7-14:
+ * Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@xxxxxxxxxxxxxx>
+ */
+
+#include <linux/time.h>
+#include <linux/module.h>
+
+/*
+ * Nonzero if YEAR is a leap year (every 4 years,
+ * except every 100th isn't, and every 400th is).
+ */
+static inline int __isleap(unsigned int year)
+{
+ return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);
+}
The explicit `inline' probably isn't beneficial here.
OK, I'll remove it.
+/* How many days come before each month (0-12). */
+static const unsigned short __mon_yday[2][13] =
+ {
+ /* Normal years. */
+ {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
+ /* Leap years. */
+ {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
+ };
+
+#define SECS_PER_HOUR (60 * 60)
+#define SECS_PER_DAY (SECS_PER_HOUR * 24)
I wonder if these whould be in a header. I guess not, if there aren't
any sites which can use this.
Agree, IMHO, it is not necessary to move it into header.
+static void __offtime(__kernel_time_t totalsecs, int offset,
+ unsigned int *year, unsigned int *mon, unsigned int *mday,
+ unsigned int *hour, unsigned int *min, unsigned int *sec,
+ unsigned int *wday, unsigned int *yday)
+{
+ long days, rem, y;
+ const unsigned short *ip;
+
+ days = totalsecs / SECS_PER_DAY;
+ rem = totalsecs % SECS_PER_DAY;
+ rem += offset;
+ while (rem < 0) {
+ rem += SECS_PER_DAY;
+ --days;
+ }
+ while (rem >= SECS_PER_DAY) {
+ rem -= SECS_PER_DAY;
+ ++days;
+ }
+
+ if (hour)
+ *hour = rem / SECS_PER_HOUR;
+ rem %= SECS_PER_HOUR;
+ if (min)
+ *min = rem / 60;
+ if (sec)
+ *sec = rem % 60;
+
+ if (wday) {
+ /* January 1, 1970 was a Thursday. */
+ *wday = (4 + days) % 7;
+ if (*wday < 0)
+ *wday += 7;
+ }
The code should all be converted to standard kernel style, please. Mainly the use of hard tabs.
Sorry, I'll resend this patch.
+ y = 1970;
+
+#define DIV(a, b) ((a) / (b) - ((a) % (b) < 0))
hm, I wonder what that does.
It would be clearer to convert this into a regular C function, along
with a comment whcih explains what it does.
+#define LEAPS_THRU_END_OF(y) (DIV(y, 4) - DIV(y, 100) + DIV(y, 400))
Ditto.
It is because I try to keep similar style with code in glibc so that updates
in glibc can easy to applied here.
But actually it looks ugly, I'll fix it.
+ while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {
+ /* Guess a corrected year, assuming 365 days per year. */
+ long yg = y + days / 365 - (days % 365 < 0);
+
+ /* Adjust DAYS and Y to match the guessed year. */
+ days -= ((yg - y) * 365
+ + LEAPS_THRU_END_OF(yg - 1)
+ - LEAPS_THRU_END_OF(y - 1));
+ y = yg;
+ }
+ if (year) {
+ *year = y - 1900;
+ if (*year != y - 1900) {
+ /* The year cannot be represented due to overflow. */
+ *year = -1;
+ }
+ }
+
+ if (yday)
+ *yday = days;
+
+ ip = __mon_yday[__isleap(y)];
+ for (y = 11; days < ip[y]; y--)
+ continue;
+ days -= ip[y];
+ if (mon)
+ *mon = y;
+ if (mday)
+ *mday = days + 1;
+}
...
+void gmtime(__kernel_time_t totalsecs,
+ unsigned int *year, unsigned int *mon, unsigned int *mday,
+ unsigned int *hour, unsigned int *min, unsigned int *sec,
+ unsigned int *wday, unsigned int *yday)
+{
+ __offtime(totalsecs, 0, year, mon, mday, hour, min, sec, wday, yday);
+}
+EXPORT_SYMBOL(gmtime);
...
+void localtime(__kernel_time_t totalsecs,
+ unsigned int *year, unsigned int *mon, unsigned int *mday,
+ unsigned int *hour, unsigned int *min, unsigned int *sec,
+ unsigned int *wday, unsigned int *yday)
+{
+ __offtime(totalsecs, -sys_tz.tz_minuteswest * 60, year, mon, mday, hour,
+ min, sec, wday, yday);
+}
+EXPORT_SYMBOL(localtime);
These are such simple wrappers around __offtime() that it might be
better to make them static inlines in time.h, so callers will end up
directly calling __offtime() rather than having to remarshal ten
function arguments.
Good idea, will fix.
Thanks
Zhaolei
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