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SubjectRe: [TIP,BISECTED] Negative nice values have become big positive numbers
On Mon, Mar 09, 2009 at 08:08:24AM +0100, Ingo Molnar wrote:
>
> * Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Sun, 8 Mar 2009, Sitsofe Wheeler wrote:
> >
> > > (Forgot to cc lkml. Resending...)
> > >
> > > Formally negative nice values have started become very big in positive
> > > integers in -tip kernels:
> > >
> > > 2 root 15 2147483647 0 0 0 S 0.0 0.0 0:00.00 kthreadd
> >
> > Is this the output of top?
>
> seems so.
>
> > > I've just finished bisecting down to this commit:
> > >
> > > commit 1427cdf0592368bdec57276edaf714040ee8744f
> > > Author: Lai Jiangshan <laijs@cn.fujitsu.com>
> > > Date: Fri Mar 6 17:21:47 2009 +0100
> >
> > $ git show 1427cdf0592368bdec57276edaf714040ee8744f | diffstat
> > include/linux/ftrace.h | 3 +
> > kernel/trace/Kconfig | 6 ++
> > kernel/trace/Makefile | 1
> > kernel/trace/trace.c | 56 +++++++++++++++++++++++++++
> > kernel/trace/trace.h | 12 +++++
> > kernel/trace/trace_bprintk.c | 87
> > +++++++++++++++++++++++++++++++++++++++++++
> > kernel/trace/trace_output.c | 75 +++++++++++++++++++++++++++++++++++++
> > 7 files changed, 240 insertions(+)
> >
> > I find it hard to believe that this would cause normal nice
> > values to be messed up. The only file that could could come
> > close to messing with nice values in top is ftrace.h:
>
> Correct - maybe it's these two nearby commits that cause the
> problems:
>
> fef20d9: vsprintf: unify the format decoding layer for its 3 users
> 4370aa4: vsprintf: add binary printf
>
> they do affect generic code. If we broke vsnprintf (which the
> nice value output code uses) then that might be a plausible
> explanation.
>
> Ingo


Thanks for this report Sitsofe. I have some ideas about the origin of this bug.
Anyway I'm in the middle of moving to another town. There are very good chances
that I send a fix tomorrow but not today.

Thanks.



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