Messages in this thread | | | Date | Fri, 20 Jul 2012 07:36:57 -0700 | From | "Paul E. McKenney" <> | Subject | Re: WARNING: at kernel/rcutree.c:1550 __rcu_process_callbacks+0x46f/0x4b0() |
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On Fri, Jul 20, 2012 at 04:11:00PM +0530, Srivatsa S. Bhat wrote: > On 07/19/2012 10:45 PM, Paul E. McKenney wrote: > > On Thu, Jul 19, 2012 at 05:39:30PM +0530, Srivatsa S. Bhat wrote: > >> Hi Paul, > >> > >> While running a CPU hotplug stress test on v3.5-rc7+ > >> (mainline commit 8a7298b7805ab) I hit this warning. > >> I haven't tried to debug this yet... > >> > >> Line number 1550 maps to: > >> > >> WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); > >> > >> inside rcu_do_batch(). > > > > Hello, Srivatsa, > > > > I believe that you need commit a16b7a69 (Prevent __call_rcu() from > > invoking RCU core on offline CPUs), which is currently in -tip, queued > > for 3.6. Please see below for the patch. > > > > Does this help? > > Yes, that fixed it, thanks! :-) > Sorry for the noise...
May I add your Tested-by?
Thanx, Paul
> Regards, > Srivatsa S. Bhat > > > > > ------------------------------------------------------------------------ > > > > rcu: Prevent __call_rcu() from invoking RCU core on offline CPUs > > > > The __call_rcu() function will invoke the RCU core, for example, if > > it detects that the current CPU has too many callbacks. However, this > > can happen on an offline CPU that is on its way to the idle loop, in > > which case it is an error to invoke the RCU core, and the excess callbacks > > will be adopted in any case. This commit therefore adds checks to > > __call_rcu() for running on an offline CPU, refraining from invoking > > the RCU core in this case. > > > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Reviewed-by: Josh Triplett <josh@joshtriplett.org> > > > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index a4a9c91..ceaa959 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -1904,11 +1904,11 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), > > * If called from an extended quiescent state, invoke the RCU > > * core in order to force a re-evaluation of RCU's idleness. > > */ > > - if (rcu_is_cpu_idle()) > > + if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) > > invoke_rcu_core(); > > > > - /* If interrupts were disabled, don't dive into RCU core. */ > > - if (irqs_disabled_flags(flags)) { > > + /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ > > + if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) { > > local_irq_restore(flags); > > return; > > } > >
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