almost a patch for 2.4.19: /proc/sys/kernel/time

["Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de>]

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Hello,

I have a patch known as "PPSkit" that converts the kernel to use an 
internal time base of nanoseconds for wall time...

Some time ago (1999) I implemented a new sysctl directory 
/proc/sys/kernel/time that allows fixing some of the oddities having to 
do with time (e.g. setting the timezone, preventing the kernel from 
doing RTC updates, forcing the kernel to do RTC updates when the clock 
is set, etc.)

With the recent discussion about "HZ", I decided to implement 
/proc/sys/kernel/time/Hz as read-only variable.

I'll attach a part of the patch against 2.4.19 that was ripped out of 
"PPSpatch-2.4.19.gz" (that I uploaded today to the kernel master 
directory ...kernel.org:/pub/linux/daemons/ntp/PPS). The file is time-
sysctl.diff (6kB).

The patch against kernel/time.c will not work, but that's only lines to 
add. Leave out all variables that you don't know, and you should still 
get a working subset.

The documentation refers to the "PPSkit" version, so ignore any 
"nanosecond", or read it as "microsecond". I'd like to hear some 
comments about the idea.

Please mail directly to me too as I'm nut subscribed to linux-kernel.

Thanks & regards,
Ulrich Windl


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Index: include/linux/sysctl.h
===================================================================
RCS file: /root/LinuxCVS/Kernel/include/linux/sysctl.h,v
retrieving revision 1.1.1.7
retrieving revision 1.1.1.7.2.2
diff -u -r1.1.1.7 -r1.1.1.7.2.2
--- include/linux/sysctl.h	18 Aug 2002 20:12:08 -0000	1.1.1.7
+++ include/linux/sysctl.h	17 Oct 2002 20:02:05 -0000	1.1.1.7.2.2
@@ -124,8 +124,20 @@
 	KERN_CORE_USES_PID=52,		/* int: use core or core.%pid */
 	KERN_TAINTED=53,	/* int: various kernel tainted flags */
 	KERN_CADPID=54,		/* int: PID of the process to notify on CAD */
+	KERN_TIME=55,		/* directory: time */
 };
 
+/* KERN_TIME names: */
+enum
+{
+	KERN_TIME_TIMEZONE=1,		/* struct: timezone */
+	KERN_TIME_RTC_UPDATE=2,		/* int: rtc_update */
+	KERN_TIME_RTC_RUNS_LOCALTIME=3,	/* int: rtc_runs_localtime */
+	KERN_TIME_TIME_TICK=4,		/* int: time_tick */
+	KERN_TIME_TICKADJ=5,		/* int: tickadj */
+	KERN_TIME_HZ=6,			/* int: HZ */
+	KERN_TIME_PPS_VAR=99,		/* struct pps_var: pps */
+};
 
 /* CTL_VM names: */
 enum
# the following patch was edited!
Index: kernel/time.c
===================================================================
RCS file: /root/LinuxCVS/Kernel/kernel/time.c,v
retrieving revision 1.1.1.4
retrieving revision 1.1.1.4.2.3
diff -u -r1.1.1.4 -r1.1.1.4.2.3
--- kernel/time.c	18 Aug 2002 20:12:14 -0000	1.1.1.4
+++ kernel/time.c	17 Oct 2002 20:06:20 -0000	1.1.1.4.2.3
@@ -7,28 +7,185 @@
+/* Define entries for `time' subdirectory. */
+static /* const */ int	sysctl_tz_min	= -12 * 60;
+static /* const */ int	sysctl_tz_max	=  12 * 60;
+static /* const */ int	sysctl_zero	= 0;
+static /* const */ int	sysctl_one	= 1;
+static /* const */ int	sysctl_no_max	= 1 << 30;
+static /* const */ int	sysctl_tick_min	= 9 * (NANOSECOND/10/hz);
+static /* const */ int	sysctl_tick_max	= 11 * (NANOSECOND/10/hz);
+static /* const */ int	sysctl_tickadj_max = (NANOSECOND/hz) / 4;
+static /* const */ int	sysctl_hz = HZ;
+
+ctl_table kern_time_table[] = {
+	/* Warning: ``sys_tz.tz_dsttime'' isn't checked properly */
+	{KERN_TIME_TIMEZONE, "timezone", &sys_tz, sizeof(sys_tz),
+	 0644, NULL, &proc_dointvec_minmax, NULL, NULL,
+	 &sysctl_tz_min, &sysctl_tz_max},
+	{KERN_TIME_RTC_RUNS_LOCALTIME, "rtc_runs_localtime",
+	 &rtc_runs_localtime, sizeof(rtc_runs_localtime),
+	 0644, NULL, &proc_dointvec_minmax, NULL, NULL,
+	 &sysctl_zero, &sysctl_one},
+	{KERN_TIME_RTC_UPDATE, "rtc_update", &rtc_update, sizeof(rtc_update),
+	 0644, NULL, &proc_dointvec_minmax, NULL, NULL,
+	 &sysctl_zero, &sysctl_no_max},
+	{KERN_TIME_TIME_TICK, "time_tick", &time_tick, sizeof(time_tick),
+	 0644, NULL, &proc_dointvec_minmax, NULL, NULL,
+	 &sysctl_tick_min, &sysctl_tick_max},
+	{KERN_TIME_TICKADJ, "tickadj", &tickadj, sizeof(tickadj),
+	 0644, NULL, &proc_dointvec_minmax, NULL, NULL,
+	 &sysctl_one, &sysctl_tickadj_max},
+	{KERN_TIME_HZ, "Hz", &sysctl_hz, sizeof(sysctl_hz),
+	 0444, NULL, &proc_dointvec},
+#ifdef CONFIG_NTP
+#ifdef CONFIG_NTP_PPS
+	/* this entry is for debugging (experimental) */
+	{KERN_TIME_PPS_VAR, "pps", &pps, sizeof(pps),
+	 0444, NULL, &proc_dointvec},
+#endif
+#endif
+	{0}
+};
+
Index: Documentation/sysctl/kernel.txt
===================================================================
RCS file: /root/LinuxCVS/Kernel/Documentation/sysctl/kernel.txt,v
retrieving revision 1.1.1.2
retrieving revision 1.1.1.2.6.2
diff -u -r1.1.1.2 -r1.1.1.2.6.2
--- Documentation/sysctl/kernel.txt	13 Dec 2001 18:48:49 -0000	1.1.1.2
+++ Documentation/sysctl/kernel.txt	17 Oct 2002 20:14:21 -0000	1.1.1.2.6.2
@@ -40,6 +40,7 @@
 - sg-big-buff                 [ generic SCSI device (sg) ]
 - shmmax                      [ sysv ipc ]
 - tainted
+- time			      [ directory ]
 - version
 - zero-paged                  [ PPC only ]
 
@@ -218,6 +219,37 @@
 on the maximum shared memory segment size that can be created.
 Shared memory segments up to 1Gb are now supported in the 
 kernel.  This value defaults to SHMMAX.
+
+==============================================================
+
+time:
+
+time/Hz (r/o):
+	Intended to reveal the value of HZ to user programs.
+
+time/pps (r/o):
+	(experimental) Used to reveal the internals of ``struct pps''
+
+time/rtc_runs_localtime (r/w):
+	Set to ``1'' if RTC is set to local time
+
+time/rtc_update (r/w):
+	Amount of seconds after which the RTC is updated from system time
+	if ``STA_UNSYNC'' in ``time_status'' is cleared.  When setting the
+	system time directly, it will be updated the next second.
+	Setting ``rtc_update'' to a value <= 0, the RTC is not updated.
+
+time/tickadj (r/w):
+	Amount of nanoseconds that will be used to adjust a wrong clock
+	gradually (using ``adjtime()'').
+
+time/time_tick (r/w):
+	Amount of nanoseconds to add every timer interrupt.
+
+time/timezone (r/w):
+	Two values describing the time zone offset west of GMT in minutes,
+	and whether daylight saving time is active (required to convert
+	kernel time to local time).
 
 ==============================================================
 
Index: kernel/sysctl.c
===================================================================
RCS file: /root/LinuxCVS/Kernel/kernel/sysctl.c,v
retrieving revision 1.1.1.11
retrieving revision 1.1.1.11.2.1
diff -u -r1.1.1.11 -r1.1.1.11.2.1
--- kernel/sysctl.c	18 Aug 2002 20:12:14 -0000	1.1.1.11
+++ kernel/sysctl.c	19 Aug 2002 20:36:01 -0000	1.1.1.11.2.1
@@ -14,6 +14,7 @@
  * Added proc_doulongvec_minmax, 09/08/99, Carlos H. Bauer.
  * Changed linked lists to use list.h instead of lists.h, 02/24/00, Bill
  *  Wendling.
+ * Added `time' subdirectory, 11/09/99, Ulrich Windl
  * The list_for_each() macro wasn't appropriate for the sysctl loop.
  *  Removed it and replaced it with older style, 03/23/00, Bill Wendling
  */
@@ -108,6 +109,7 @@
 	{ root_table, LIST_HEAD_INIT(root_table_header.ctl_entry) };
 
 static ctl_table kern_table[];
+extern ctl_table kern_time_table[];
 static ctl_table vm_table[];
 #ifdef CONFIG_NET
 extern ctl_table net_table[];
@@ -256,6 +258,7 @@
 	{KERN_S390_USER_DEBUG_LOGGING,"userprocess_debug",
 	 &sysctl_userprocess_debug,sizeof(int),0644,NULL,&proc_dointvec},
 #endif
+	{KERN_TIME, "time", NULL, 0, 0555, kern_time_table},
 	{0}
 };