Messages in this thread |  | | | Date | Tue, 12 Jul 2011 22:15:40 +0100 | | Subject | Re: PROBLEM: 3.0-rc kernels unbootable since -rc3 | | From | Julie Sullivan <> |
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On Mon, Jul 11, 2011 at 10:43 PM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > On Mon, Jul 11, 2011 at 09:37:53PM +0100, julie Sullivan wrote: >> > And here is what I am proposing sending upstream. I have your Tested-by, >> > but had to make a small but very real change in order to make it work >> > under all configurations that I test under. So could you please try >> > the attached patch out? I am particularly interested in how it works >> > out when CONFIG_RCU_BOOST=n. >> > >> > 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) >> > >> >> Hi Paul, >> Is this to be applied on a clean v3.0-rc4? I tried this but I'm afraid >> the boot crash is back again (on -rc5 and -rc6 too). > > I must confess that it did seem to be giving up a bit too easily. :-( > > So, I have created a new branch jms.2011.07.11a on the -rcu git tree at: > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git > > If the new branch jms.2011.07.11a fails and the old branch jms.2011.07.07a > succeeds (both with CONFIG_RCU_BOOST=n), then that indicates that my > mainlinable patch didn't delay the callbacks quite far enough. On the > other hand, if both succeed, then that means that there is another bug > lurking later on in the sequence of commits. > > Could you please test these out? > > Thanx, Paul >
OK tested- jms.2011.07.11a fails. The other one's fine (I'm actually running an -rc6 with its patches right now :-)
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