From: Paul E. McKenney Date: Wed, 28 Feb 2018 18:34:54 +0000 (-0800) Subject: rcu: Don't allocate rcu_nocb_mask if no one needs it X-Git-Tag: v4.19~927^2~1^2^2~11 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ef12620626e4e6a062acd9701d1d3429b2356773;p=platform%2Fkernel%2Flinux-rpi.git rcu: Don't allocate rcu_nocb_mask if no one needs it Commit 44c65ff2e3b0 ("rcu: Eliminate NOCBs CPU-state Kconfig options") made allocation of rcu_nocb_mask depend only on the rcu_nocbs=, nohz_full=, or isolcpus= kernel boot parameters. However, it failed to change the initial value of rcu_init_nohz()'s local variable need_rcu_nocb_mask to false, which can result in useless allocation of an all-zero rcu_nocb_mask. This commit therefore fixes this bug by changing the initial value of need_rcu_nocb_mask to false. While we are in the area, also correct the error message that is printed when someone specifies that can-never-exist CPUs should be NOCBs CPUs. Reported-by: Byungchul Park Signed-off-by: Paul E. McKenney Acked-by: Byungchul Park Tested-by: Nicholas Piggin --- diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 6c5df18..3566e4f 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2283,7 +2283,7 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) void __init rcu_init_nohz(void) { int cpu; - bool need_rcu_nocb_mask = true; + bool need_rcu_nocb_mask = false; struct rcu_state *rsp; #if defined(CONFIG_NO_HZ_FULL) @@ -2306,7 +2306,7 @@ void __init rcu_init_nohz(void) #endif /* #if defined(CONFIG_NO_HZ_FULL) */ if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { - pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); + pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); cpumask_and(rcu_nocb_mask, cpu_possible_mask, rcu_nocb_mask); }