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    SubjectRe: [PATCH 02/16] rcu: Check return value for cpumask allocation
    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");

    --
    Pranith


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