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Date: Sun, 11 Nov 2001 18:33:32 +0100 (CET)
From: Tim Schmielau <tim@physik3.uni-rostock.de>
To: Linus Torvalds <torvalds@transmeta.com>
cc: <linux-kernel@vger.kernel.org>, J Sloan <jjs@lexus.com>,
        Petr Vandrovec <VANDROVE@vc.cvut.cz>,
        george anzinger <george@mvista.com>,
        "Richard B. Johnson" <root@chaos.analogic.com>,
        Benjamin LaHaise <bcrl@redhat.com>
Subject: [Patch] enable uptime display > 497 days
Message-ID: <Pine.LNX.4.30.0111111803120.11130-100000@gans.physik3.uni-rostock.de>
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Sender: linux-kernel-owner@vger.kernel.org
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Dear Linus,

the appended patch enables 32 bit linux boxes to display more than
497.1 days of uptime. No user land application changes are needed.
This is the solution that came out of the "[Patch] Re: Nasty suprise with
uptime" thread a week ago.

As no objections have been raised since then, and as I was able to cure
the observed lockups after jiffies wraparound by the "[Patch] fix
incorrect jiffies compares" just posted to lkml, I believe this to be
ready for inclusion into the main tree.


The patch introduces a get_jiffies64() function that internally counts the
jiffies wrap. This way there is no overhead neither in the timer interrupt
nor in functions not interested in a 64bit jiffies value. IMHO this patch
does not interfere with the possible introduction of a "real" 64 bit
jiffies counter at later times, as the get_jiffies64() can still be
retained then to provide the necessary locking.

I also extended the start_time field of struct task_struct to 64 bits so
that ps output will still be ok after the 32 bit wraparound while keeping
sub-second resolution of runtimes.

Idle time overflow is dealt with in the same way as the jiffies
wraparound. The CPU time of the idle task will still overflow as it will
for every other process getting more than 497.1 days of CPU time, but I
don't want to blow up every time variable. I believe this to be acceptable
behavior.

The downshot of counting jiffies wraps in get_jiffies64() is that
overflows get undetected if for more than 497 days
 - /proc/uptime is not read,
 - sysinfo() is not called,
 - and no new processes are started,
which altogether is rather unlikely.


Correct uptime display after jiffies wrap is of course only useful if
there are no stability problems after the wrap. To aid in finding out this
I added a config time option to initialize the jiffies counter to a value
5 minutes before wrap. I kindly ask people to turn this on and watch out.
It did not affect stability for me anymore after the jiffies comparison
fixed were applied.

Tim



diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/Documentation/Configure.help linux-2.4.15-pre2-jiffies64/Documentation/Configure.help
--- linux-2.4.15-pre2/Documentation/Configure.help	Sun Nov 11 10:23:36 2001
+++ linux-2.4.15-pre2-jiffies64/Documentation/Configure.help	Sun Nov 11 10:40:13 2001
@@ -23550,6 +23550,14 @@
   of the BUG call as well as the EIP and oops trace.  This aids
   debugging but costs about 70-100K of memory.

+Debug jiffies counter wraparound (DANGEROUS)
+CONFIG_DEBUG_JIFFIESWRAP
+  Say Y here to initialize the jiffies counter to a value 5 minutes
+  before wraparound. This may make your system UNSTABLE and its
+  only use is to hunt down the causes of this instability.
+  If you don't know what the jiffies counter is or if you want
+  a stable system, say N.
+
 Include kgdb kernel debugger
 CONFIG_KGDB
   Include in-kernel hooks for kgdb, the Linux kernel source level
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/arm/config.in linux-2.4.15-pre2-jiffies64/arch/arm/config.in
--- linux-2.4.15-pre2/arch/arm/config.in	Sun Nov 11 10:23:36 2001
+++ linux-2.4.15-pre2-jiffies64/arch/arm/config.in	Sun Nov 11 10:40:13 2001
@@ -601,6 +601,7 @@
 bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
 bool 'Spinlock debugging' CONFIG_DEBUG_SPINLOCK
 dep_bool 'Disable pgtable cache' CONFIG_NO_PGT_CACHE $CONFIG_CPU_26
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 # These options are only for real kernel hackers who want to get their hands dirty.
 dep_bool 'Kernel low-level debugging functions' CONFIG_DEBUG_LL $CONFIG_EXPERIMENTAL
 dep_bool '  Kernel low-level debugging messages via footbridge serial port' CONFIG_DEBUG_DC21285_PORT $CONFIG_DEBUG_LL $CONFIG_FOOTBRIDGE
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/cris/config.in linux-2.4.15-pre2-jiffies64/arch/cris/config.in
--- linux-2.4.15-pre2/arch/cris/config.in	Mon Oct 15 22:42:14 2001
+++ linux-2.4.15-pre2-jiffies64/arch/cris/config.in	Sun Nov 11 10:40:13 2001
@@ -250,4 +250,5 @@
 if [ "$CONFIG_PROFILE" = "y" ]; then
   int ' Profile shift count' CONFIG_PROFILE_SHIFT 2
 fi
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/i386/config.in linux-2.4.15-pre2-jiffies64/arch/i386/config.in
--- linux-2.4.15-pre2/arch/i386/config.in	Sat Nov  3 02:46:47 2001
+++ linux-2.4.15-pre2-jiffies64/arch/i386/config.in	Sun Nov 11 10:40:13 2001
@@ -405,6 +405,7 @@
    bool '  Magic SysRq key' CONFIG_MAGIC_SYSRQ
    bool '  Spinlock debugging' CONFIG_DEBUG_SPINLOCK
    bool '  Verbose BUG() reporting (adds 70K)' CONFIG_DEBUG_BUGVERBOSE
+   bool '  Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 fi

 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/m68k/config.in linux-2.4.15-pre2-jiffies64/arch/m68k/config.in
--- linux-2.4.15-pre2/arch/m68k/config.in	Tue Jun 12 04:15:27 2001
+++ linux-2.4.15-pre2-jiffies64/arch/m68k/config.in	Sun Nov 11 10:40:13 2001
@@ -545,4 +545,5 @@

 #bool 'Debug kmalloc/kfree' CONFIG_DEBUG_MALLOC
 bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/mips/config.in linux-2.4.15-pre2-jiffies64/arch/mips/config.in
--- linux-2.4.15-pre2/arch/mips/config.in	Mon Oct 15 22:41:34 2001
+++ linux-2.4.15-pre2-jiffies64/arch/mips/config.in	Sun Nov 11 10:40:13 2001
@@ -519,4 +519,5 @@
 if [ "$CONFIG_SMP" != "y" ]; then
    bool 'Run uncached' CONFIG_MIPS_UNCACHED
 fi
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/parisc/config.in linux-2.4.15-pre2-jiffies64/arch/parisc/config.in
--- linux-2.4.15-pre2/arch/parisc/config.in	Wed Apr 18 02:19:25 2001
+++ linux-2.4.15-pre2-jiffies64/arch/parisc/config.in	Sun Nov 11 10:40:13 2001
@@ -206,5 +206,6 @@

 #bool 'Debug kmalloc/kfree' CONFIG_DEBUG_MALLOC
 bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu

diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/ppc/config.in linux-2.4.15-pre2-jiffies64/arch/ppc/config.in
--- linux-2.4.15-pre2/arch/ppc/config.in	Sat Nov  3 02:43:54 2001
+++ linux-2.4.15-pre2-jiffies64/arch/ppc/config.in	Sun Nov 11 10:40:13 2001
@@ -391,4 +391,5 @@
 bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
 bool 'Include kgdb kernel debugger' CONFIG_KGDB
 bool 'Include xmon kernel debugger' CONFIG_XMON
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/sh/config.in linux-2.4.15-pre2-jiffies64/arch/sh/config.in
--- linux-2.4.15-pre2/arch/sh/config.in	Mon Oct 15 22:36:48 2001
+++ linux-2.4.15-pre2-jiffies64/arch/sh/config.in	Sun Nov 11 10:40:13 2001
@@ -385,4 +385,5 @@
 if [ "$CONFIG_SH_STANDARD_BIOS" = "y" ]; then
    bool 'Early printk support' CONFIG_SH_EARLY_PRINTK
 fi
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/arch/sparc/config.in linux-2.4.15-pre2-jiffies64/arch/sparc/config.in
--- linux-2.4.15-pre2/arch/sparc/config.in	Tue Jun 12 04:15:27 2001
+++ linux-2.4.15-pre2-jiffies64/arch/sparc/config.in	Sun Nov 11 10:40:13 2001
@@ -265,4 +265,5 @@
 comment 'Kernel hacking'

 bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
+bool 'Debug jiffies counter wraparound (DANGEROUS)' CONFIG_DEBUG_JIFFIESWRAP
 endmenu
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/fs/proc/array.c linux-2.4.15-pre2-jiffies64/fs/proc/array.c
--- linux-2.4.15-pre2/fs/proc/array.c	Thu Oct 11 18:00:01 2001
+++ linux-2.4.15-pre2-jiffies64/fs/proc/array.c	Sun Nov 11 10:40:13 2001
@@ -343,7 +343,7 @@
 	ppid = task->pid ? task->p_opptr->pid : 0;
 	read_unlock(&tasklist_lock);
 	res = sprintf(buffer,"%d (%s) %c %d %d %d %d %d %lu %lu \
-%lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %lu %lu %ld %lu %lu %lu %lu %lu \
+%lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %llu %lu %ld %lu %lu %lu %lu %lu \
 %lu %lu %lu %lu %lu %lu %lu %lu %d %d\n",
 		task->pid,
 		task->comm,
@@ -366,7 +366,7 @@
 		nice,
 		0UL /* removed */,
 		task->it_real_value,
-		task->start_time,
+		(unsigned long long)(task->start_time) - INITIAL_JIFFIES,
 		vsize,
 		mm ? mm->rss : 0, /* you might want to shift this left 3 */
 		task->rlim[RLIMIT_RSS].rlim_cur,
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/fs/proc/proc_misc.c linux-2.4.15-pre2-jiffies64/fs/proc/proc_misc.c
--- linux-2.4.15-pre2/fs/proc/proc_misc.c	Thu Oct 11 19:46:57 2001
+++ linux-2.4.15-pre2-jiffies64/fs/proc/proc_misc.c	Sun Nov 11 10:40:14 2001
@@ -39,6 +39,7 @@
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/io.h>
+#include <asm/div64.h>


 #define LOAD_INT(x) ((x) >> FSHIFT)
@@ -100,37 +101,59 @@
 	return proc_calc_metrics(page, start, off, count, eof, len);
 }

+#if BITS_PER_LONG < 48
+
+u64 get_idle64(void)
+{
+	static unsigned long idle_hi, idle_last;
+	static spinlock_t idle64_lock = SPIN_LOCK_UNLOCKED;
+	unsigned long idle;
+
+	spin_lock(&idle64_lock);
+	idle = init_tasks[0]->times.tms_utime + init_tasks[0]->times.tms_stime;
+	if (idle < idle_last)   /* We have a wrap */
+		idle_hi++;
+	idle_last = idle;
+	spin_unlock(&idle64_lock);
+
+	return (idle | ((u64)idle_hi) << BITS_PER_LONG);
+}
+
+#else
+ /* Idle time won't overflow for 8716 years at HZ==1024 */
+
+static inline u64 get_idle64(void)
+{
+	return (u64)(init_tasks[0]->times.tms_utime
+	             + init_tasks[0]->times.tms_stime);
+}
+
+#endif /* BITS_PER_LONG < 48 */
+
 static int uptime_read_proc(char *page, char **start, off_t off,
 				 int count, int *eof, void *data)
 {
-	unsigned long uptime;
-	unsigned long idle;
+	u64 uptime, idle;
+	unsigned long uptime_remainder, idle_remainder;
 	int len;

-	uptime = jiffies;
-	idle = init_tasks[0]->times.tms_utime + init_tasks[0]->times.tms_stime;
+	uptime = get_jiffies64() - INITIAL_JIFFIES;
+	uptime_remainder = (unsigned long) do_div(uptime, HZ);
+	idle = get_idle64();
+	idle_remainder = (unsigned long) do_div(idle, HZ);

-	/* The formula for the fraction parts really is ((t * 100) / HZ) % 100, but
-	   that would overflow about every five days at HZ == 100.
-	   Therefore the identity a = (a / b) * b + a % b is used so that it is
-	   calculated as (((t / HZ) * 100) + ((t % HZ) * 100) / HZ) % 100.
-	   The part in front of the '+' always evaluates as 0 (mod 100). All divisions
-	   in the above formulas are truncating. For HZ being a power of 10, the
-	   calculations simplify to the version in the #else part (if the printf
-	   format is adapted to the same number of digits as zeroes in HZ.
-	 */
 #if HZ!=100
 	len = sprintf(page,"%lu.%02lu %lu.%02lu\n",
-		uptime / HZ,
-		(((uptime % HZ) * 100) / HZ) % 100,
-		idle / HZ,
-		(((idle % HZ) * 100) / HZ) % 100);
+		(unsigned long) uptime,
+		(uptime_remainder * 100) / HZ,
+		(unsigned long) idle,
+		(idle_remainder * 100) / HZ);
 #else
 	len = sprintf(page,"%lu.%02lu %lu.%02lu\n",
-		uptime / HZ,
-		uptime % HZ,
-		idle / HZ,
-		idle % HZ);
+		(unsigned long) uptime,
+		uptime_remainder,
+		(unsigned long) idle,
+		idle_remainder);
 #endif
 	return proc_calc_metrics(page, start, off, count, eof, len);
 }
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/include/linux/sched.h linux-2.4.15-pre2-jiffies64/include/linux/sched.h
--- linux-2.4.15-pre2/include/linux/sched.h	Sun Nov 11 10:28:23 2001
+++ linux-2.4.15-pre2-jiffies64/include/linux/sched.h	Sun Nov 11 12:59:22 2001
@@ -352,7 +352,7 @@
 	unsigned long it_real_incr, it_prof_incr, it_virt_incr;
 	struct timer_list real_timer;
 	struct tms times;
-	unsigned long start_time;
+	u64 start_time;
 	long per_cpu_utime[NR_CPUS], per_cpu_stime[NR_CPUS];
 /* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
 	unsigned long min_flt, maj_flt, nswap, cmin_flt, cmaj_flt, cnswap;
@@ -549,6 +549,8 @@
 #include <asm/current.h>

 extern unsigned long volatile jiffies;
+extern u64 get_jiffies64(void);
+
 extern unsigned long itimer_ticks;
 extern unsigned long itimer_next;
 extern struct timeval xtime;
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/include/linux/timex.h linux-2.4.15-pre2-jiffies64/include/linux/timex.h
--- linux-2.4.15-pre2/include/linux/timex.h	Mon Nov  5 21:42:13 2001
+++ linux-2.4.15-pre2-jiffies64/include/linux/timex.h	Sun Nov 11 12:54:00 2001
@@ -53,6 +53,13 @@

 #include <asm/param.h>

+#ifdef CONFIG_DEBUG_JIFFIESWRAP
+  /* Make the jiffies counter wrap around sooner. */
+# define INITIAL_JIFFIES ((unsigned long)(-300*HZ))
+#else
+# define INITIAL_JIFFIES 0
+#endif
+
 /*
  * The following defines establish the engineering parameters of the PLL
  * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/kernel/acct.c linux-2.4.15-pre2-jiffies64/kernel/acct.c
--- linux-2.4.15-pre2/kernel/acct.c	Mon Mar 19 21:35:08 2001
+++ linux-2.4.15-pre2-jiffies64/kernel/acct.c	Sun Nov 11 10:40:14 2001
@@ -56,6 +56,7 @@
 #include <linux/tty.h>

 #include <asm/uaccess.h>
+#include <asm/div64.h>

 /*
  * These constants control the amount of freespace that suspend and
@@ -227,20 +228,24 @@
  *  This routine has been adopted from the encode_comp_t() function in
  *  the kern_acct.c file of the FreeBSD operating system. The encoding
  *  is a 13-bit fraction with a 3-bit (base 8) exponent.
+ *
+ *  Bumped up to encode 64 bit values. Unfortunately the result may
+ *  overflow now.
  */

 #define	MANTSIZE	13			/* 13 bit mantissa. */
-#define	EXPSIZE		3			/* Base 8 (3 bit) exponent. */
+#define	EXPSIZE		3			/* 3 bit exponent. */
+#define	EXPBASE		3			/* Base 8 (3 bit) exponent. */
 #define	MAXFRACT	((1 << MANTSIZE) - 1)	/* Maximum fractional value. */

-static comp_t encode_comp_t(unsigned long value)
+static comp_t encode_comp_t(u64 value)
 {
 	int exp, rnd;

 	exp = rnd = 0;
 	while (value > MAXFRACT) {
-		rnd = value & (1 << (EXPSIZE - 1));	/* Round up? */
-		value >>= EXPSIZE;	/* Base 8 exponent == 3 bit shift. */
+		rnd = value & (1 << (EXPBASE - 1));	/* Round up? */
+		value >>= EXPBASE;	/* Base 8 exponent == 3 bit shift. */
 		exp++;
 	}

@@ -248,16 +253,21 @@
          * If we need to round up, do it (and handle overflow correctly).
          */
 	if (rnd && (++value > MAXFRACT)) {
-		value >>= EXPSIZE;
+		value >>= EXPBASE;
 		exp++;
 	}

 	/*
          * Clean it up and polish it off.
          */
-	exp <<= MANTSIZE;		/* Shift the exponent into place */
-	exp += value;			/* and add on the mantissa. */
-	return exp;
+	if (exp >= (1 << EXPSIZE)) {
+		/* Overflow. Return largest representable number instead. */
+		return (1ul << (MANTSIZE + EXPSIZE)) - 1;
+	} else {
+		exp <<= MANTSIZE;	/* Shift the exponent into place */
+		exp += value;		/* and add on the mantissa. */
+		return exp;
+	}
 }

 /*
@@ -277,6 +287,7 @@
 	struct acct ac;
 	mm_segment_t fs;
 	unsigned long vsize;
+	u64 elapsed;

 	/*
 	 * First check to see if there is enough free_space to continue
@@ -294,8 +305,10 @@
 	strncpy(ac.ac_comm, current->comm, ACCT_COMM);
 	ac.ac_comm[ACCT_COMM - 1] = '\0';

-	ac.ac_btime = CT_TO_SECS(current->start_time) + (xtime.tv_sec - (jiffies / HZ));
-	ac.ac_etime = encode_comp_t(jiffies - current->start_time);
+	elapsed = get_jiffies64() - current->start_time;
+	ac.ac_etime = encode_comp_t(elapsed);
+	do_div(elapsed, HZ);
+	ac.ac_btime = xtime.tv_sec - elapsed;
 	ac.ac_utime = encode_comp_t(current->times.tms_utime);
 	ac.ac_stime = encode_comp_t(current->times.tms_stime);
 	ac.ac_uid = current->uid;
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/kernel/fork.c linux-2.4.15-pre2-jiffies64/kernel/fork.c
--- linux-2.4.15-pre2/kernel/fork.c	Wed Oct 24 02:44:15 2001
+++ linux-2.4.15-pre2-jiffies64/kernel/fork.c	Sun Nov 11 10:40:14 2001
@@ -647,7 +647,7 @@
 	}
 #endif
 	p->lock_depth = -1;		/* -1 = no lock */
-	p->start_time = jiffies;
+	p->start_time = get_jiffies64();

 	INIT_LIST_HEAD(&p->local_pages);

diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/kernel/info.c linux-2.4.15-pre2-jiffies64/kernel/info.c
--- linux-2.4.15-pre2/kernel/info.c	Sat Apr 21 01:15:40 2001
+++ linux-2.4.15-pre2-jiffies64/kernel/info.c	Sun Nov 11 10:40:14 2001
@@ -12,15 +12,19 @@
 #include <linux/smp_lock.h>

 #include <asm/uaccess.h>
+#include <asm/div64.h>

 asmlinkage long sys_sysinfo(struct sysinfo *info)
 {
 	struct sysinfo val;
+	u64 uptime;

 	memset((char *)&val, 0, sizeof(struct sysinfo));

 	cli();
-	val.uptime = jiffies / HZ;
+	uptime = get_jiffies64() - INITIAL_JIFFIES;
+	do_div(uptime, HZ);
+	val.uptime = (unsigned long) uptime;

 	val.loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT);
 	val.loads[1] = avenrun[1] << (SI_LOAD_SHIFT - FSHIFT);
diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/kernel/timer.c linux-2.4.15-pre2-jiffies64/kernel/timer.c
--- linux-2.4.15-pre2/kernel/timer.c	Mon Oct  8 19:41:41 2001
+++ linux-2.4.15-pre2-jiffies64/kernel/timer.c	Sun Nov 11 13:05:25 2001
@@ -65,7 +65,7 @@

 extern int do_setitimer(int, struct itimerval *, struct itimerval *);

-unsigned long volatile jiffies;
+unsigned long volatile jiffies = INITIAL_JIFFIES;

 unsigned int * prof_buffer;
 unsigned long prof_len;
@@ -115,9 +115,17 @@
 	}
 	for (i = 0; i < TVR_SIZE; i++)
 		INIT_LIST_HEAD(tv1.vec + i);
+
+#if CONFIG_DEBUG_JIFFIESWRAP
+	tv1.index = INITIAL_JIFFIES & TVR_MASK;
+	tv2.index = (INITIAL_JIFFIES >> TVR_BITS) & TVN_MASK;
+	tv3.index = (INITIAL_JIFFIES >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
+	tv4.index = (INITIAL_JIFFIES >> (TVR_BITS + 2*TVN_BITS)) & TVN_MASK;
+	tv5.index = (INITIAL_JIFFIES >> (TVR_BITS + 3*TVN_BITS)) & TVN_MASK;
+#endif
 }

-static unsigned long timer_jiffies;
+static unsigned long timer_jiffies = INITIAL_JIFFIES;

 static inline void internal_add_timer(struct timer_list *timer)
 {
@@ -638,7 +646,7 @@
 }

 /* jiffies at the most recent update of wall time */
-unsigned long wall_jiffies;
+unsigned long wall_jiffies = INITIAL_JIFFIES;

 /*
  * This spinlock protect us from races in SMP while playing with xtime. -arca
@@ -683,6 +691,37 @@
 	if (TQ_ACTIVE(tq_timer))
 		mark_bh(TQUEUE_BH);
 }
+
+
+#if BITS_PER_LONG < 48
+
+u64 get_jiffies64(void)
+{
+	static unsigned long jiffies_hi = 0;
+	static unsigned long jiffies_last = INITIAL_JIFFIES;
+	static spinlock_t jiffies64_lock = SPIN_LOCK_UNLOCKED;
+	unsigned long jiffies_tmp;
+
+	spin_lock(&jiffies64_lock);
+	jiffies_tmp = jiffies;   /* avoid races */
+	if (jiffies_tmp < jiffies_last)   /* We have a wrap */
+		jiffies_hi++;
+	jiffies_last = jiffies_tmp;
+	spin_unlock(&jiffies64_lock);
+
+	return (jiffies_tmp | ((u64)jiffies_hi) << BITS_PER_LONG);
+}
+
+#else
+ /* jiffies is wide enough to not wrap for 8716 years at HZ==1024 */
+
+static inline u64 get_jiffies64(void)
+{
+	return (u64)jiffies;
+}
+
+#endif /* BITS_PER_LONG < 48 */
+

 #if !defined(__alpha__) && !defined(__ia64__)

diff -u -r --exclude-from dontdiff linux-2.4.15-pre2/mm/oom_kill.c linux-2.4.15-pre2-jiffies64/mm/oom_kill.c
--- linux-2.4.15-pre2/mm/oom_kill.c	Sun Nov  4 02:05:25 2001
+++ linux-2.4.15-pre2-jiffies64/mm/oom_kill.c	Sun Nov 11 10:42:26 2001
@@ -69,11 +69,10 @@
 	/*
 	 * CPU time is in seconds and run time is in minutes. There is no
 	 * particular reason for this other than that it turned out to work
-	 * very well in practice. This is not safe against jiffie wraps
-	 * but we don't care _that_ much...
+	 * very well in practice.
 	 */
 	cpu_time = (p->times.tms_utime + p->times.tms_stime) >> (SHIFT_HZ + 3);
-	run_time = (jiffies - p->start_time) >> (SHIFT_HZ + 10);
+	run_time = (get_jiffies64() - p->start_time) >> (SHIFT_HZ + 10);

 	points /= int_sqrt(cpu_time);
 	points /= int_sqrt(int_sqrt(run_time));

-
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