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SubjectRe: [PATCH tip/core/rcu 0/2] rcu: fixes for RCU lockdep

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> On Fri, Feb 26, 2010 at 12:50:18PM +0100, Ingo Molnar wrote:
> >
> > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> >
> > > Hello!
> > >
> > > This set fixes a couple of problems with the RCU-based lockdep patches:
> > >
> > > 1. Make the lockdep_rcu_dereference() message less alarmist
> > >
> > > 2. Make rcu_read_lock_sched_held() take boot-time lack of
> > > preemption into account.
> > >
> > > Thanx, Paul
> > >
> > > ------------------------------------------------------------------------
> > >
> > > include/linux/rcupdate.h | 4 +++-
> > > include/linux/rcutiny.h | 4 ----
> > > include/linux/rcutree.h | 1 -
> > > kernel/lockdep.c | 7 +++----
> > > kernel/rcupdate.c | 18 ++++++++++++++++++
> > > kernel/rcutree.c | 20 --------------------
> > > 6 files changed, 24 insertions(+), 30 deletions(-)
> >
> > Applied, thanks Paul!
> >
> > Here's a new warning:
> >
> > [ 0.000000]
> > [ 0.000000] ===================================================
> > [ 0.000000] [ INFO: suspicious rcu_dereference_check() usage. ]
> > [ 0.000000] ---------------------------------------------------
> > [ 0.000000] kernel/sched_fair.c:3469 invoked rcu_dereference_check() without protection!
>
> Hmmm... Could you please tell me what commit this test ran against?

One version of tip:master :-/

ob'kconfig - i think this header bit of the .config:

> > # Automatically generated make config: don't edit
> > # Linux kernel version: 2.6.33
> > # Fri Feb 26 14:51:28 2010

should contain the last-seen kernel Git sha1 as well. It would ease things
considerably.

> My guesses thus far either don't have that many lines in kernel/sched_fair.c
> or have some unrelated code at line 3469.

I'll post the sha1 next time i encounter this warning.

Thanks,

Ingo


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