Re: rcu_init allocation failure trace on bootup

[Paul E. McKenney]

On Mon, May 06, 2013 at 01:09:22PM -0700, Yinghai Lu wrote:
> On Mon, May 6, 2013 at 12:43 PM, Paul E. McKenney
> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> > On Mon, May 06, 2013 at 03:26:53PM -0400, Dave Jones wrote:
> >> On Mon, May 06, 2013 at 12:05:22PM -0700, Paul E. McKenney wrote:
> >>  > On Mon, May 06, 2013 at 01:56:47PM -0400, Dave Jones wrote:
> >>  > > [    0.000000]  RCU debugfs-based tracing is enabled.
> >>  > > [    0.000000]  RCU lockdep checking is enabled.
> >>  > > [    0.000000] ------------[ cut here ]------------
> >>  > > [    0.000000] WARNING: at mm/nobootmem.c:215 ___alloc_bootmem_nopanic+0x3a/0x7d()
> >>  > > [    0.000000] Modules linked in:
> >>  > > [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.9.0+ #128
> >>  > > [    0.000000] Hardware name:                  /D975XBX, BIOS BX97510J.86A.1209.2006.0601.1340 06/01/2006
> >>  > > [    0.000000]  ffffffff819f4246 ffffffff81c01e68 ffffffff816a0db2 ffffffff81c01ea8
> >>  > > [    0.000000]  ffffffff8104b1a0 ffffffff819e1078 0000000000000000 0000000000000008
> >>  > > [    0.000000]  ffffffffffffffff 0000000000000040 0000000000000000 ffffffff81c01eb8
> >>  > > [    0.000000] Call Trace:
> >>  > > [    0.000000]  [<ffffffff816a0db2>] dump_stack+0x19/0x1b
> >>  > > [    0.000000]  [<ffffffff8104b1a0>] warn_slowpath_common+0x70/0xa0
> >>  > > [    0.000000]  [<ffffffff8104b1ea>] warn_slowpath_null+0x1a/0x20
> >>  > > [    0.000000]  [<ffffffff81ef8914>] ___alloc_bootmem_nopanic+0x3a/0x7d
> >>  > > [    0.000000]  [<ffffffff81ef8b87>] __alloc_bootmem+0x13/0x39
> >>  > > [    0.000000]  [<ffffffff81f090ad>] alloc_bootmem_cpumask_var+0x1a/0x21
> >>  > > [    0.000000]  [<ffffffff81ef1f5a>] rcu_init+0x7f/0x261
> >>  > > [    0.000000]  [<ffffffff81ef4acb>] ? perf_event_init+0x178/0x181
> >>  > > [    0.000000]  [<ffffffff81ed6c79>] start_kernel+0x232/0x3d3
> >>  > > [    0.000000]  [<ffffffff81ed6846>] ? repair_env_string+0x5e/0x5e
> >>  > > [    0.000000]  [<ffffffff81ed6577>] x86_64_start_reservations+0x2a/0x2c
> >>  > > [    0.000000]  [<ffffffff81ed6646>] x86_64_start_kernel+0xcd/0xd1
> >>  > > [    0.000000] ---[ end trace 0acfc82c197165dd ]---
> >>  > > [    0.000000]  Experimental no-CBs for all CPUs
> >>  > > [    0.000000]  Experimental no-CBs CPUs: 0-1.
> >>  > > [    0.000000] NO_HZ: Full dynticks CPUs: 1.
> >>  >
> >>  > Do you have commit fa0f93cd6a (rcu: Don't allocate bootmem from rcu_init())?
> >>  > If not, could you please try applying it?
> >>
> >> That commit isn't in Linus tree.
> >
> > You are quite right, I am getting ahead of myself.  Please see below
> > for the patch.
> >
> >                                                         Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > rcu: Don't allocate bootmem from rcu_init()
> >
> > When rcu_init() is called we already have slab working, allocating
> > bootmem at that point results in warnings and an allocation from
> > slab.  This commit therefore changes alloc_bootmem_cpumask_var() to
> > alloc_cpumask_var() in rcu_bootup_announce_oddness(), which is called
> > from rcu_init().
> >
> > Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> >
> > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> > index ca6e39c..44b0998 100644
> > --- a/kernel/rcutree_plugin.h
> > +++ b/kernel/rcutree_plugin.h
> > @@ -86,7 +86,7 @@ static void __init rcu_bootup_announce_oddness(void)
> >  #ifdef CONFIG_RCU_NOCB_CPU
> >  #ifndef CONFIG_RCU_NOCB_CPU_NONE
> >         if (!have_rcu_nocb_mask) {
> > -               alloc_bootmem_cpumask_var(&rcu_nocb_mask);
> > +               alloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL);
> 
> Do you need to use zalloc_cpumask_var instead?

Good point!  I have queued up a fix for this.

							Thanx, Paul

> >                 have_rcu_nocb_mask = true;
> >         }
> >  #ifdef CONFIG_RCU_NOCB_CPU_ZERO
> >
> > --
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