scale_stime() silently assumes that stime < rtime, otherwise when
stime == rtime and both values are big (operations on them do not fit
in 32 bits), the resulting scaling stime can be bigger than rtime.
In consequence utime = rtime - stime results in negative value.
Reported-and-tested-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
Cc: sta...@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgrus...@redhat.com>
---
kernel/sched/cputime.c | 19 +++++++++++--------
1 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index ace34f9..9994791 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -551,10 +551,7 @@ static void cputime_adjust(struct task_cputime *curr,
struct cputime *prev,
cputime_t *ut, cputime_t *st)
{
- cputime_t rtime, stime, utime, total;
-
- stime = curr->stime;
- total = stime + curr->utime;
+ cputime_t rtime, stime, utime;
/*
* Tick based cputime accounting depend on random scheduling
@@ -576,13 +573,19 @@ static void cputime_adjust(struct task_cputime *curr,
if (prev->stime + prev->utime >= rtime)
goto out;
- if (total) {
+ stime = curr->stime;
+ utime = curr->utime;
+
+ if (utime == 0) {
+ stime = rtime;
+ } else if (stime == 0) {
+ utime = rtime;
+ } else {
+ cputime_t total = stime + utime;
+
stime = scale_stime((__force u64)stime,
(__force u64)rtime, (__force u64)total);
utime = rtime - stime;
- } else {
- stime = rtime;
- utime = 0;
}
/*
--
1.7.1
--
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