From: john stultz Since jiffies didn't necessarily start incrementing at a second boundary, jiffies/HZ doesn't increment at the same moment as xtime.tv_sec. This causes one second wobbles in the calculation of btime (xtime.tv_sec - jiffies/HZ). This fix increases the precision of the calculation so the usec component of xtime is used as well. Additionally it fixes some of the non-atomic reading of time values. This is a fix for bugme bug #764. http://bugme.osdl.org/show_bug.cgi?id=764 25-akpm/fs/proc/proc_misc.c | 19 ++++++++++++++++--- 1 files changed, 16 insertions(+), 3 deletions(-) diff -puN fs/proc/proc_misc.c~proc-stat-btime-fix fs/proc/proc_misc.c --- 25/fs/proc/proc_misc.c~proc-stat-btime-fix Tue Jun 3 16:15:07 2003 +++ 25-akpm/fs/proc/proc_misc.c Tue Jun 3 16:15:07 2003 @@ -378,8 +378,22 @@ static int kstat_read_proc(char *page, c { 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() - INITIAL_JIFFIES; + do_gettimeofday(&now); + } while (read_seqretry(&xtime_lock, seq)); + + /* calc # of seconds since boot time */ + 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 +433,6 @@ static int kstat_read_proc(char *page, c 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 +440,7 @@ static int kstat_read_proc(char *page, c "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()); _