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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-02-28 10:34:54 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-05-15 10:27:11 -0700
commitef12620626e4e6a062acd9701d1d3429b2356773 (patch)
treec71cd47c517e568645b766067da600bcaf34a612
parentbe01b4cab118e7a2d9747c71b3bef8f28fdda193 (diff)
downloadlinux-ef12620626e4e6a062acd9701d1d3429b2356773.tar.bz2
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 <byungchul.park@lge.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Byungchul Park <byungchul.park@lge.com> Tested-by: Nicholas Piggin <npiggin@gmail.com>
-rw-r--r--kernel/rcu/tree_plugin.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6c5df18bbf2f..3566e4f6dfcc 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);
}