* Stanislaw Gruszka <sgrus...@redhat.com> wrote:
> scale_stime() silently assumes that stime < rtime, otherwise when
> stime == rtime and both values are big enough (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.
>
> User space visible symptoms of the bug are overflowed TIME values on
> ps/top, for example:
>
> ps aux | grep rcu
> root 8 0.0 0.0 0 0 ? S 12:42 0:00 [rcuc/0]
> root 9 0.0 0.0 0 0 ? S 12:42 0:00 [rcub/0]
> root 10 62422329 0.0 0 0 ? R 12:42 21114581:37
> [rcu_preempt]
> root 11 0.1 0.0 0 0 ? S 12:42 0:02 [rcuop/0]
> root 12 62422329 0.0 0 0 ? S 12:42 21114581:35
> [rcuop/1]
> root 10 62422329 0.0 0 0 ? R 12:42 21114581:37
> [rcu_preempt]
>
> or overflowed utime values read directly from /proc/$PID/stat
>
> Reference:
> https://lkml.org/lkml/2013/8/20/259
>
> Reported-and-tested-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
> Cc: sta...@vger.kernel.org
> Signed-off-by: Stanislaw Gruszka <sgrus...@redhat.com>
> ---
> v1 -> v2 : describe user visible symptoms of the bug
>
> kernel/sched/cputime.c | 19 +++++++++++--------
> 1 files changed, 11 insertions(+), 8 deletions(-)
Applied, thanks!
Ingo
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