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Date: Sun, 18 Nov 2001 12:57:01 +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>,
        Andreas Dilger <adilger@turbolabs.com>
Subject: Re: [Patch] enable uptime display > 497 days
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[new patch further down]

> 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.
>
[...]
> 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 go 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.

I extended the patch to use a counter for periodically checking for
jiffies overflows, so none can go undetected anymore. Still the CPU time
overhead is minimal as timer are implemented rather efficiently

> 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
> fixes were applied.

Tim


diff -u -r --exclude-from dontdiff linux-2.4.15-pre6/Documentation/Configure.help linux-2.4.15-pre6-jiffies64/Documentation/Configure.help
--- linux-2.4.15-pre6/Documentation/Configure.help	Sun Nov 18 10:41:30 2001
+++ linux-2.4.15-pre6-jiffies64/Documentation/Configure.help	Sun Nov 18 10:42:12 2001
@@ -23579,6 +23579,14 @@
   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-pre6/arch/arm/config.in linux-2.4.15-pre6-jiffies64/arch/arm/config.in
--- linux-2.4.15-pre6/arch/arm/config.in	Sun Nov 18 10:41:30 2001
+++ linux-2.4.15-pre6-jiffies64/arch/arm/config.in	Sun Nov 18 10:42:12 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 $CONFIG_FOOTBRIDGE
diff -u -r --exclude-from dontdiff linux-2.4.15-pre6/arch/cris/config.in linux-2.4.15-pre6-jiffies64/arch/cris/config.in
--- linux-2.4.15-pre6/arch/cris/config.in	Mon Oct 15 22:42:14 2001
+++ linux-2.4.15-pre6-jiffies64/arch/cris/config.in	Sun Nov 18 10:42:12 2001
@@ -250,4 +250,5 @@
 if [ "$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-pre6/arch/i386/config.in linux-2.4.15-pre6-jiffies64/arch/i386/config.in
--- linux-2.4.15-pre6/arch/i386/config.in	Sun Nov 18 10:41:30 2001
+++ linux-2.4.15-pre6-jiffies64/arch/i386/config.in	Sun Nov 18 10:42:12 2001
@@ -407,6 +407,7 @@
    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-pre6/arch/m68k/config.in linux-2.4.15-pre6-jiffies64/arch/m68k/config.in
--- linux-2.4.15-pre6/arch/m68k/config.in	Tue Jun 12 04:15:27 2001
+++ linux-2.4.15-pre6-jiffies64/arch/m68k/config.in	Sun Nov 18 10:42:12 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-pre6/arch/mips/config.in linux-2.4.15-pre6-jiffies64/arch/mips/config.in
--- linux-2.4.15-pre6/arch/mips/config.in	Mon Oct 15 22:41:34 2001
+++ linux-2.4.15-pre6-jiffies64/arch/mips/config.in	Sun Nov 18 10:42:12 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-pre6/arch/parisc/config.in linux-2.4.15-pre6-jiffies64/arch/parisc/config.in
--- linux-2.4.15-pre6/arch/parisc/config.in	Wed Apr 18 02:19:25 2001
+++ linux-2.4.15-pre6-jiffies64/arch/parisc/config.in	Sun Nov 18 10:42:12 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-pre6/arch/ppc/config.in linux-2.4.15-pre6-jiffies64/arch/ppc/config.in
--- linux-2.4.15-pre6/arch/ppc/config.in	Sun Nov 18 10:41:30 2001
+++ linux-2.4.15-pre6-jiffies64/arch/ppc/config.in	Sun Nov 18 10:42:12 2001
@@ -392,4 +392,5 @@
 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-pre6/arch/sh/config.in linux-2.4.15-pre6-jiffies64/arch/sh/config.in
--- linux-2.4.15-pre6/arch/sh/config.in	Mon Oct 15 22:36:48 2001
+++ linux-2.4.15-pre6-jiffies64/arch/sh/config.in	Sun Nov 18 10:42:12 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-pre6/arch/sparc/config.in linux-2.4.15-pre6-jiffies64/arch/sparc/config.in
--- linux-2.4.15-pre6/arch/sparc/config.in	Tue Jun 12 04:15:27 2001
+++ linux-2.4.15-pre6-jiffies64/arch/sparc/config.in	Sun Nov 18 10:42:12 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-pre6/fs/proc/array.c linux-2.4.15-pre6-jiffies64/fs/proc/array.c
--- linux-2.4.15-pre6/fs/proc/array.c	Thu Oct 11 18:00:01 2001
+++ linux-2.4.15-pre6-jiffies64/fs/proc/array.c	Sun Nov 18 10:42:12 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-pre6/fs/proc/proc_misc.c linux-2.4.15-pre6-jiffies64/fs/proc/proc_misc.c
--- linux-2.4.15-pre6/fs/proc/proc_misc.c	Sun Nov 18 10:41:35 2001
+++ linux-2.4.15-pre6-jiffies64/fs/proc/proc_misc.c	Sun Nov 18 10:42:12 2001
@@ -40,6 +40,7 @@
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/io.h>
+#include <asm/div64.h>


 #define LOAD_INT(x) ((x) >> FSHIFT)
@@ -98,37 +99,59 @@
 	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-pre6/include/linux/sched.h linux-2.4.15-pre6-jiffies64/include/linux/sched.h
--- linux-2.4.15-pre6/include/linux/sched.h	Sun Nov 18 10:41:37 2001
+++ linux-2.4.15-pre6-jiffies64/include/linux/sched.h	Sun Nov 18 11:41:06 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-pre6/include/linux/timex.h linux-2.4.15-pre6-jiffies64/include/linux/timex.h
--- linux-2.4.15-pre6/include/linux/timex.h	Mon Nov  5 21:42:13 2001
+++ linux-2.4.15-pre6-jiffies64/include/linux/timex.h	Sun Nov 18 11:41:06 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-pre6/kernel/acct.c linux-2.4.15-pre6-jiffies64/kernel/acct.c
--- linux-2.4.15-pre6/kernel/acct.c	Mon Mar 19 21:35:08 2001
+++ linux-2.4.15-pre6-jiffies64/kernel/acct.c	Sun Nov 18 10:42:12 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-pre6/kernel/fork.c linux-2.4.15-pre6-jiffies64/kernel/fork.c
--- linux-2.4.15-pre6/kernel/fork.c	Wed Oct 24 02:44:15 2001
+++ linux-2.4.15-pre6-jiffies64/kernel/fork.c	Sun Nov 18 10:42:12 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-pre6/kernel/info.c linux-2.4.15-pre6-jiffies64/kernel/info.c
--- linux-2.4.15-pre6/kernel/info.c	Sat Apr 21 01:15:40 2001
+++ linux-2.4.15-pre6-jiffies64/kernel/info.c	Sun Nov 18 10:42:12 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-pre6/kernel/timer.c linux-2.4.15-pre6-jiffies64/kernel/timer.c
--- linux-2.4.15-pre6/kernel/timer.c	Mon Oct  8 19:41:41 2001
+++ linux-2.4.15-pre6-jiffies64/kernel/timer.c	Sun Nov 18 12:34:16 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;
@@ -103,6 +103,8 @@

 #define NOOF_TVECS (sizeof(tvecs) / sizeof(tvecs[0]))

+static inline void init_jiffieswrap_timer(void);
+
 void init_timervecs (void)
 {
 	int i;
@@ -115,9 +117,19 @@
 	}
 	for (i = 0; i < TVR_SIZE; i++)
 		INIT_LIST_HEAD(tv1.vec + i);
+
+#ifdef 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
+
+	init_jiffieswrap_timer();
 }

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

 static inline void internal_add_timer(struct timer_list *timer)
 {
@@ -638,7 +650,7 @@
 }

 /* 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 +695,60 @@
 	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, flags;
+
+	spin_lock_irqsave(&jiffies64_lock, flags);
+	jiffies_tmp = jiffies;   /* avoid races */
+	if (jiffies_tmp < jiffies_last)   /* We have a wrap */
+		jiffies_hi++;
+	jiffies_last = jiffies_tmp;
+	spin_unlock_irqrestore(&jiffies64_lock, flags);
+
+	return (jiffies_tmp | ((u64)jiffies_hi) << BITS_PER_LONG);
+}
+
+/* use a timer to periodically check for jiffies overflows */
+
+static struct timer_list jiffieswrap_timer;
+#define CHECK_JIFFIESWRAP_INTERVAL 0x7ffffffful
+
+static void check_jiffieswrap(void)
+{
+	mod_timer(&jiffieswrap_timer, jiffies + CHECK_JIFFIESWRAP_INTERVAL);
+	get_jiffies64();
+}
+
+static inline void init_jiffieswrap_timer(void)
+{
+	init_timer(&jiffieswrap_timer);
+	jiffieswrap_timer.expires = jiffies + CHECK_JIFFIESWRAP_INTERVAL;
+	jiffieswrap_timer.function = check_jiffieswrap;
+	add_timer(&jiffieswrap_timer);
+}
+
+#else
+ /* jiffies is wide enough to not wrap for 8716 years at HZ==1024 */
+
+static inline u64 get_jiffies64(void)
+{
+	return (u64)jiffies;
+}
+
+static inline void init_jiffieswrap_timer(void)
+{
+}
+
+#endif /* BITS_PER_LONG < 48 */
+

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

diff -u -r --exclude-from dontdiff linux-2.4.15-pre6/mm/oom_kill.c linux-2.4.15-pre6-jiffies64/mm/oom_kill.c
--- linux-2.4.15-pre6/mm/oom_kill.c	Sun Nov  4 02:05:25 2001
+++ linux-2.4.15-pre6-jiffies64/mm/oom_kill.c	Sun Nov 18 10:42:12 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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