From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Julie Sullivan <kernelmail.jms@gmail.com>
Cc: linux-kernel-mail <linux-kernel@vger.kernel.org>
Subject: Re: PROBLEM: 3.0-rc kernels unbootable since -rc3
Date: Tue, 12 Jul 2011 14:29:20 -0700 [thread overview]
Message-ID: <20110712212920.GQ2326@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAAVPGOOJ0NEWqF2w9zCLC1bpXeA_TwzenNo-a4kvR3tcbewnNw@mail.gmail.com>
On Tue, Jul 12, 2011 at 10:15:40PM +0100, Julie Sullivan wrote:
> 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 :-)
Just to make sure I understand what patch you are using... Is it the
one that I have listed below? It would be bad form for me to send the
wrong patch upstream. ;-)
If this is the correct one, then the upstreamable patch I sent recently
(https://lkml.org/lkml/2011/7/12/313) should also work. Famous last
words...
Thanx, Paul
------------------------------------------------------------------------
rcu: prevent RCU callbacks from being invoked during early boot.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index dbe4120..4456395 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1476,7 +1476,7 @@ 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_kthreads_spawnable && !rsp->boost)) {
rcu_do_batch(rsp, rdp);
return;
}
next prev parent reply other threads:[~2011-07-12 21:29 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-06 21:10 PROBLEM: 3.0-rc kernels unbootable since -rc3 julie Sullivan
2011-07-06 21:23 ` Paul E. McKenney
2011-07-07 19:31 ` Paul E. McKenney
2011-07-07 19:47 ` julie Sullivan
2011-07-07 19:58 ` Paul E. McKenney
2011-07-07 20:28 ` julie Sullivan
2011-07-07 20:47 ` julie Sullivan
2011-07-08 0:29 ` Paul E. McKenney
2011-07-09 10:09 ` Paul E. McKenney
2011-07-10 0:45 ` julie Sullivan
2011-07-10 3:25 ` Paul E. McKenney
2011-07-10 16:38 ` julie Sullivan
2011-07-10 17:16 ` Paul E. McKenney
2011-07-10 17:35 ` Paul E. McKenney
2011-07-10 20:30 ` julie Sullivan
2011-07-10 21:46 ` Paul E. McKenney
2011-07-10 21:50 ` julie Sullivan
2011-07-10 23:14 ` Paul E. McKenney
2011-07-11 16:24 ` Konrad Rzeszutek Wilk
2011-07-11 17:13 ` Paul E. McKenney
2011-07-11 19:30 ` Konrad Rzeszutek Wilk
2011-07-11 20:15 ` Paul E. McKenney
2011-07-11 21:09 ` Konrad Rzeszutek Wilk
2011-07-12 10:55 ` Paul E. McKenney
2011-07-12 14:12 ` Konrad Rzeszutek Wilk
2011-07-12 14:49 ` Paul E. McKenney
2011-07-12 15:07 ` Paul E. McKenney
2011-07-12 15:15 ` Paul E. McKenney
2011-07-12 15:22 ` Paul E. McKenney
2011-07-12 16:32 ` PROBLEM: 3.0-rc kernels unbootable since -rc3 - under Xen, 32-bit guest only Konrad Rzeszutek Wilk
2011-07-12 16:46 ` Paul E. McKenney
2011-07-12 16:03 ` PROBLEM: 3.0-rc kernels unbootable since -rc3 Konrad Rzeszutek Wilk
2011-07-12 16:39 ` Paul E. McKenney
2011-07-12 18:01 ` Konrad Rzeszutek Wilk
2011-07-12 18:59 ` Paul E. McKenney
2011-07-12 19:07 ` Konrad Rzeszutek Wilk
2011-07-12 20:52 ` Paul E. McKenney
2011-07-12 19:10 ` Peter Zijlstra
2011-07-12 19:57 ` Konrad Rzeszutek Wilk
2011-07-12 20:46 ` Paul E. McKenney
2011-07-12 21:04 ` Julie Sullivan
2011-07-12 21:07 ` Paul E. McKenney
2011-07-12 20:05 ` Paul E. McKenney
2011-07-12 6:33 ` [Xen-devel] " Sander Eikelenboom
2011-07-12 14:05 ` Paul E. McKenney
[not found] ` <CAAVPGOMSprJSkzziH6hJv9PweOONzsMaRZEK2ZSrV3xFBReTPw@mail.gmail.com>
[not found] ` <20110711214301.GP2245@linux.vnet.ibm.com>
2011-07-12 21:15 ` Julie Sullivan
2011-07-12 21:29 ` Paul E. McKenney [this message]
2011-07-12 21:35 ` Julie Sullivan
2011-07-12 21:49 ` Julie Sullivan
2011-07-12 22:00 ` Paul E. McKenney
2011-07-13 7:18 ` RKK
2011-07-13 15:47 ` Paul E. McKenney
2011-07-13 20:57 ` Julie Sullivan
2011-07-13 21:23 ` Paul E. McKenney
2011-07-07 17:28 ` julie Sullivan
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