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SubjectRe: [PATCH v2 1/2] rcu: Create a function for rcu_nocb_mask boot time setup
On Thu, Jul 24, 2014 at 08:37:31PM -0400, Pranith Kumar wrote:
> This commit creates a function rcu_bootup_announce_oddness_nocb(), which handles
> allocation of rcu_nocb_mask and setting it according to the kernel configuration
> parameters.
>
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>

Much better!

One more change called out below.

Thanx, Paul

> ---
> v2: don't break the print string (comment from paulmck)
>
> kernel/rcu/tree_plugin.h | 61 +++++++++++++++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 26 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index c31eb28..520538a 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -47,6 +47,39 @@ static char __initdata nocb_buf[NR_CPUS * 5];
> #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
>
> /*
> + * This is a helper for rcu_bootup_announce_oddness(), which takes care of
> + * setting up rcu_nocb_mask for nocb specific kernel configuration parameters
> + */
> +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);
> + have_rcu_nocb_mask = true;
> + }
> +#ifdef CONFIG_RCU_NOCB_CPU_ZERO
> + pr_info("\tOffload RCU callbacks from CPU 0\n");
> + cpumask_set_cpu(0, rcu_nocb_mask);
> +#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
> +#ifdef CONFIG_RCU_NOCB_CPU_ALL
> + pr_info("\tOffload RCU callbacks from all CPUs\n");
> + 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");
> + }
> +}
> +
> +/*
> * Check the RCU kernel configuration parameters and print informative
> * messages about anything out of the ordinary. If you like #ifdef, you
> * will love this function.
> @@ -86,32 +119,8 @@ static void __init rcu_bootup_announce_oddness(void)
> if (nr_cpu_ids != NR_CPUS)
> pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
> #ifdef CONFIG_RCU_NOCB_CPU

Please also move the above #ifdef into rcu_bootup_announce_oddness_nocb().
The compiler will inline the resulting empty function, and it is cleaner
to have all of the NOCB-related #ifdefs in that function.

> -#ifndef CONFIG_RCU_NOCB_CPU_NONE
> - if (!have_rcu_nocb_mask) {
> - zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL);
> - have_rcu_nocb_mask = true;
> - }
> -#ifdef CONFIG_RCU_NOCB_CPU_ZERO
> - pr_info("\tOffload RCU callbacks from CPU 0\n");
> - cpumask_set_cpu(0, rcu_nocb_mask);
> -#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
> -#ifdef CONFIG_RCU_NOCB_CPU_ALL
> - pr_info("\tOffload RCU callbacks from all CPUs\n");
> - 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");
> - }
> -#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
> + rcu_bootup_announce_oddness_nocb();
> +#endif
> }
>
> #ifdef CONFIG_TREE_PREEMPT_RCU
> --
> 2.0.1
>



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