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fix cputime overflow in uptime_proc_show

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commit c3e0ef9a29 upstream.

For 32-bit architectures using standard jiffies the idletime calculation
in uptime_proc_show will quickly overflow. It takes (2^32 / HZ) seconds
of idle-time, or e.g. 12.45 days with no load on a quad-core with HZ=1000.
Switch to 64-bit calculations.

Cc: Michael Abbott <michael.abbott@diamond.ac.uk>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Martin Schwidefsky
2011-12-15 14:56:10 +01:00
committed by Greg Kroah-Hartman
parent 277a05f83a
commit 3ec3f83aee
1 changed files with 7 additions and 2 deletions
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9
fs/proc/uptime.c
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@@ -11,15 +11,20 @@ static int uptime_proc_show(struct seq_file *m, void *v)
{
struct timespec uptime;
struct timespec idle;
cputime64_t idletime;
u64 nsec;
u32 rem;
int i;
cputime_t idletime = cputime_zero;
idletime = 0;
for_each_possible_cpu(i)
idletime = cputime64_add(idletime, kstat_cpu(i).cpustat.idle);
do_posix_clock_monotonic_gettime(&uptime);
monotonic_to_bootbased(&uptime);
cputime_to_timespec(idletime, &idle);
nsec = cputime64_to_jiffies64(idletime) * TICK_NSEC;
idle.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
idle.tv_nsec = rem;
seq_printf(m, "%lu.%02lu %lu.%02lu\n",
(unsigned long) uptime.tv_sec,
(uptime.tv_nsec / (NSEC_PER_SEC / 100)),