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SubjectRe: [Patch] enable uptime display > 497 days
[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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