Andrew, All,
Due to a math error in the calculation of /proc/stat's btime, the value
could wobble, varying by a single second. The patch fixes this wobble
described in bugme bug #764.
Reportedly Hans is seeing larger then 1 second wobbles which I have not
been able to reproduce, but that looks to be a separate issue to this
math bug.
Please consider for inclusion.
thanks
-john
diff -Nru a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
--- a/fs/proc/proc_misc.c Thu Jun 5 15:07:14 2003
+++ b/fs/proc/proc_misc.c Thu Jun 5 15:07:14 2003
@@ -378,8 +378,23 @@
{
int i, len;
extern unsigned long total_forks;
- u64 jif = get_jiffies_64() - INITIAL_JIFFIES;
+ u64 jif;
unsigned int sum = 0, user = 0, nice = 0, system = 0, idle = 0, iowait = 0;
+ struct timeval now;
+ unsigned long seq;
+
+ /* Atomically read jiffies and time of day */
+ do {
+ seq = read_seqbegin(&xtime_lock);
+
+ jif = get_jiffies_64();
+ do_gettimeofday(&now);
+ } while (read_seqretry(&xtime_lock, seq));
+
+ /* calc # of seconds since boot time */
+ jif -= INITIAL_JIFFIES;
+ jif = ((u64)now.tv_sec * HZ) + (now.tv_usec/(1000000/HZ)) - jif;
+ do_div(jif, HZ);
for (i = 0 ; i < NR_CPUS; i++) {
int j;
@@ -419,7 +434,6 @@
len += sprintf(page + len, " %u", kstat_irqs(i));
#endif
- do_div(jif, HZ);
len += sprintf(page + len,
"\nctxt %lu\n"
"btime %lu\n"
@@ -427,7 +441,7 @@
"procs_running %lu\n"
"procs_blocked %lu\n",
nr_context_switches(),
- xtime.tv_sec - (unsigned long) jif,
+ (unsigned long)jif,
total_forks,
nr_running(),
nr_iowait());