On Wed, Sep 04, 2013 at 07:37:22AM -0700, tip-bot for Stanislaw Gruszka wrote: > Commit-ID: 5a8e01f8fa51f5cbce8f37acc050eb2319d12956 > Gitweb: http://git.kernel.org/tip/5a8e01f8fa51f5cbce8f37acc050eb2319d12956 > Author: Stanislaw Gruszka <[email protected]> > AuthorDate: Wed, 4 Sep 2013 15:16:03 +0200 > Committer: Ingo Molnar <[email protected]> > CommitDate: Wed, 4 Sep 2013 16:31:25 +0200 > > sched/cputime: Do not scale when utime == 0 > > 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 <[email protected]> > Signed-off-by: Stanislaw Gruszka <[email protected]> > Cc: [email protected] > Cc: Frederic Weisbecker <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Borislav Petkov <[email protected]> > Link: http://lkml.kernel.org/r/[email protected] > Signed-off-by: Ingo Molnar <[email protected]>
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