Messages in this thread | | | Date | Wed, 23 Jul 2014 11:01:38 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 02/16] rcu: Check return value for cpumask allocation |
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On Wed, Jul 23, 2014 at 01:14:19PM -0400, Pranith Kumar wrote: > On Wed, Jul 23, 2014 at 8:06 AM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > >> --- a/kernel/rcu/tree_plugin.h > >> +++ b/kernel/rcu/tree_plugin.h > >> @@ -88,7 +88,10 @@ static void __init rcu_bootup_announce_oddness(void) > >> #ifdef CONFIG_RCU_NOCB_CPU > >> #ifndef CONFIG_RCU_NOCB_CPU_NONE > >> if (!have_rcu_nocb_mask) { > >> - zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL); > >> + if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { > >> + pr_info("rcu_nocb_mask allocation failed\n"); > >> + return; > > > > Good catch, but this "return" is an accident waiting to happen. The > > accident will happen as soon as another RCU option appears, and the > > person adding it quite naturally adds it at the end of this function. > > The cleanest approach is to make an rcu_bootup_announce_oddness_nocb() > > as one commit that does -only- code motion, and the make this change > > as another commit. > > > > Hi Paul, > > Looking at this, I think the following is simpler without having to > introduce a new function. What do you think? > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index c31eb28..f2ed342 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -88,8 +88,10 @@ static void __init rcu_bootup_announce_oddness(void) > #ifdef CONFIG_RCU_NOCB_CPU > #ifndef CONFIG_RCU_NOCB_CPU_NONE > if (!have_rcu_nocb_mask) { > - zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL); > - have_rcu_nocb_mask = true; > + if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) > + pr_info("rcu_nocb_mask allocation failed"); > + else > + have_rcu_nocb_mask = true; > } > #ifdef CONFIG_RCU_NOCB_CPU_ZERO > pr_info("\tOffload RCU callbacks from CPU 0\n");
I suspect that if zalloc_cpumask_var() fails, bad things will happen if we get here, at least in the CONFIG_CPUMASK_OFFSTACK=y.
Thanx, Paul
> > > -- > Pranith >
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