Messages in this thread | | | Date | Mon, 11 Jul 2011 07:17:27 -0700 | From | "Paul E. McKenney" <> | Subject | Re: Linux 3.0-rc5 doesnt boot and hangs at rcu_sched_state () |
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On Mon, Jul 11, 2011 at 07:12:25PM +0530, RKK wrote: > Hi Paul > On Mon, Jul 11, 2011 at 3:48 PM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > On Mon, Jul 11, 2011 at 10:46:30AM +0530, RKK wrote: > >> Hi Paul, > >> On Mon, Jul 11, 2011 at 9:21 AM, Paul E. McKenney > >> <paulmck@linux.vnet.ibm.com> wrote: > >> > On Sat, Jul 09, 2011 at 09:01:31AM -0700, Paul E. McKenney wrote: > >> >> On Wed, Jun 29, 2011 at 06:56:35PM +0530, RKK wrote: > >> >> > Hello, > >> >> > I tried booting Linux3.0.rc5 on my machine today but everytime it > >> >> > hangs after this message > >> >> > > >> >> > a)starting configure read only root support > >> >> > > >> >> > after this waiting for sometime then this message appears > >> >> > > >> >> > b)INFO rcu_sched_state: RCU stalls CPU/disks > >> >> > > >> >> > i tried to read the Documentation/RCU and enable CONFIG_RCU_TRACE but > >> >> > dint know how to proceed further . > >> >> > > >> >> > i tried repeating this 4-5 times , one thing i observed that is > >> >> > appearance of rcu_sched_state is intermittent but everytime the boot > >> >> > stops/hangs at a) message . > >> >> > >> >> Can you set up the SysRq key as described in Documentation/sysrq.txt? > >> >> This might help you get some information about what the system is doing > >> >> during the wait time. > >> >> > >> >> My guess is that your kernel is spinning with interrupts disabled, and > >> >> that RCU eventually tries to complain about this. The possible causes > >> >> of this are listed in Documentation/RCU/stallwarn.txt. > >> > > >> > Could you please try out this patch and see if it helps? > >> > > >> > Thanx, Paul > > > > [ . . . ] > > > >> Please give me some time as im away. i will test the patch and get > >> back to you by today evening . > >> Warm Regards > >> Ravi Kulkarni. > > > > Just as well -- I fat-fingered the patch creation. :-/ > > > > Please see below for the real patch. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > rcu: Prevent RCU callbacks from executing during early boot > > > > Under some rare but real combinations of configuration parameters, RCU > > callbacks are posted during early boot that use kernel facilities that > > are not yet initialized. Therefore, when these callbacks are invoked, > > hard hangs and crashes ensue. This commit therefore prevents RCU > > callbacks from being invoked until after the scheduler is up and running. > > > > It might well turn out that a better approach is to identify the specific > > RCU callbacks that are causing this problem, but that discussion will > > wait until such time as someone really needs an RCU callback to be > > invoked during early boot. > > > > Reported-by: julie Sullivan <kernelmail.jms@gmail.com> > > Tested-by: julie Sullivan <kernelmail.jms@gmail.com> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index 7e59ffb..4c0210f 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -1467,7 +1467,7 @@ static void rcu_process_callbacks(struct softirq_action *unused) > > */ > > static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) > > { > > - if (likely(!rsp->boost)) { > > + if (likely(rcu_scheduler_active && !rsp->boost)) { > > rcu_do_batch(rsp, rdp); > > return; > > } > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > index 14dc7dd..ca3c6dc 100644 > > --- a/kernel/rcutree_plugin.h > > +++ b/kernel/rcutree_plugin.h > > @@ -1703,7 +1703,7 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) > > > > static void invoke_rcu_callbacks_kthread(void) > > { > > - WARN_ON_ONCE(1); > > + WARN_ON_ONCE(rcu_scheduler_active); > > } > > > > static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) > > > > The above patch fixes the bug and now 3.0.rc5 is bootable :). thanks.
Thank you, Ravi! I have added your Tested-by and will now push this upstream.
Thanx, Paul
> maciej rutecki, > > can we close the the below bugzilla entry ? > https://bugzilla.kernel.org/show_bug.cgi?id=38732 > > Warm regards, > Ravi Kulkarni. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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