On Fri, Jan 22, 2016 at 09:55:44AM +0100, Geert Uytterhoeven wrote: > Hi Paul, > > On Thu, Jan 21, 2016 at 5:06 PM, Paul E. McKenney > <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Jan 21, 2016 at 02:22:56PM +0100, Geert Uytterhoeven wrote: > >> On Thu, Dec 10, 2015 at 12:10 AM, Paul E. McKenney > >> <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > >> > This commit replaces a local_irq_save()/local_irq_restore() pair with > >> > a lockdep assertion that interrupts are already disabled. This should > >> > remove the corresponding overhead from the interrupt entry/exit fastpaths. > >> > > >> > This change was inspired by the fact that Iftekhar Ahmed's mutation > >> > testing showed that removing rcu_irq_enter()'s call to local_ird_restore() > >> > had no effect, which might indicate that interrupts were always enabled > >> > anyway. > >> > > >> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > >> > --- > >> > include/linux/rcupdate.h | 4 ++-- > >> > include/linux/rcutiny.h | 8 ++++++++ > >> > include/linux/rcutree.h | 2 ++ > >> > include/linux/tracepoint.h | 4 ++-- > >> > kernel/rcu/tree.c | 32 ++++++++++++++++++++++++++------ > >> > 5 files changed, 40 insertions(+), 10 deletions(-) > >> > >> This commit (7c9906ca5e582a773fff696975e312cef58a7386) is triggering lock ups > >> during boot on r8a7791/koelsch (dual Cortex A15). Probably this commit does not > >> contain the real bug, but a symptom. > > > > On the off-chance that it is related, here is Ding Tianhong's patch > > that addressed some lockups: > > > > http://www.eenyhelp.com/patch-rfc-locking-mutexes-dont-spin-owner-when-wait-list-not-null-help-215929641.html > > > > Does that help in your case? > > Unfortunately not. We could revert the RCU patch without any real problems -- it is after all just an optimization. Hmmm... One issue that we have seen before is that the irq-disabled indication is a software flag that is not always in sync with hardware conditions. Might it be that we are hitting a situation where irqs_disabled() is giving the wrong answer, thus suppressing the lockdep warning? Thanx, Paul
