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SubjectRe: [PATCH] RCU: Remove have_rcu_nocb_mask from tree_plugin.h
On Fri, Nov 17, 2017 at 09:40:15PM +0600, Rakib Mullick wrote:
> Currently have_rcu_nocb_mask is used to avoid double allocation of
> rcu_nocb_mask during boot up. Due to different representation of
> cpumask_var_t on different kernel config CPUMASK=y(or n) it was okay.
> But now we have a helper cpumask_available(), which can be utilized
> to check whether rcu_nocb_mask has been allocated or not without using
> a variable.
>
> Removing the variable also reduces vmlinux size.
>
> Unpatched version:
> text data bss dec hex filename
> 13050393 7852470 14543408 35446271 21cddff vmlinux
>
> Patched version:
> text data bss dec hex filename
> 13050390 7852438 14543408 35446236 21cdddc vmlinux
>
> Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>

Queued for review and testing, thank you!

Thanx, Paul

> ---
> Patch applied on top of linus's tree (commit cf9b0772f2e41).
>
> kernel/rcu/tree_plugin.h | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index db85ca3..13a8e08 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -61,7 +61,6 @@ DEFINE_PER_CPU(char, rcu_cpu_has_work);
>
> #ifdef CONFIG_RCU_NOCB_CPU
> static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
> -static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */
> static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
> #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
>
> @@ -1752,7 +1751,6 @@ static void increment_cpu_stall_ticks(void)
> static int __init rcu_nocb_setup(char *str)
> {
> alloc_bootmem_cpumask_var(&rcu_nocb_mask);
> - have_rcu_nocb_mask = true;
> cpulist_parse(str, rcu_nocb_mask);
> return 1;
> }
> @@ -1801,7 +1799,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
> /* Is the specified CPU a no-CBs CPU? */
> bool rcu_is_nocb_cpu(int cpu)
> {
> - if (have_rcu_nocb_mask)
> + if (cpumask_available(rcu_nocb_mask))
> return cpumask_test_cpu(cpu, rcu_nocb_mask);
> return false;
> }
> @@ -2295,14 +2293,13 @@ void __init rcu_init_nohz(void)
> need_rcu_nocb_mask = true;
> #endif /* #if defined(CONFIG_NO_HZ_FULL) */
>
> - if (!have_rcu_nocb_mask && need_rcu_nocb_mask) {
> + if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
> if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
> pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
> return;
> }
> - have_rcu_nocb_mask = true;
> }
> - if (!have_rcu_nocb_mask)
> + if (!cpumask_available(rcu_nocb_mask))
> return;
>
> #if defined(CONFIG_NO_HZ_FULL)
> @@ -2428,7 +2425,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp)
> struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */
> struct rcu_data *rdp_prev = NULL;
>
> - if (!have_rcu_nocb_mask)
> + if (!cpumask_available(rcu_nocb_mask))
> return;
> if (ls == -1) {
> ls = int_sqrt(nr_cpu_ids);
> --
> 2.9.3
>

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