On Fri, Jul 25, 2014 at 08:25:51AM -0700, Paul E. McKenney wrote:
> On Thu, Jul 24, 2014 at 08:37:32PM -0400, Pranith Kumar wrote:
> > This commit checks the return value of the zalloc_cpumask_var() used for
> > allocating cpumask for rcu_nocb_mask.
> >
> > Signed-off-by: Pranith Kumar <[email protected]>
>
> Hmmm... I saw the check in the previous patch, but didn't see removal
> of the later have_rcu_nocb_mask check. Please see below.
And events overtook this one. Turns out that commit b58cc46c5f6b
(rcu: Don't offload callbacks unless specifically requested) was not
one of my best efforts.
I will adapt your patch 2/2 in this series and apply it with your
Signed-off-by. Patch 1/2 is obsoleted by the current fix for
commit b58cc46c5f6b.
Thanx, Paul
> > ---
> > v2: no change from v1
> >
> > kernel/rcu/tree_plugin.h | 23 ++++++++++++-----------
> > 1 file changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index 520538a..9c9a01c 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -54,7 +54,10 @@ static void __init rcu_bootup_announce_oddness_nocb(void)
> > {
> > #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;
> > + }
> > have_rcu_nocb_mask = true;
> > }
> > #ifdef CONFIG_RCU_NOCB_CPU_ZERO
> > @@ -66,17 +69,15 @@ static void __init
> > rcu_bootup_announce_oddness_nocb(void)
> > cpumask_copy(rcu_nocb_mask, cpu_possible_mask);
> > #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
> > #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
> > - if (have_rcu_nocb_mask) {
> > - if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
> > - pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains
> > nonexistent CPUs.\n");
> > - cpumask_and(rcu_nocb_mask, cpu_possible_mask,
> > - rcu_nocb_mask);
> > - }
> > - cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
> > - pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf);
> > - if (rcu_nocb_poll)
> > - pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
> > + if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
>
> What happens if CONFIG_RCU_NOCB_CPU_NONE=y and the rcu_nocbs= boot
> parameter is not specified and we get here?
>
> In order to get visible failures when testing, build with
> CONFIG_CPUMASK_OFFSTACK=y.
>
> > + pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains
> > nonexistent CPUs.\n");
> > + cpumask_and(rcu_nocb_mask, cpu_possible_mask,
> > + rcu_nocb_mask);
> > }
> > + cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
> > + pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf);
> > + if (rcu_nocb_poll)
> > + pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
> > }
> >
> > /*
> > --
> > 2.0.1
> >
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