[PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter

Frederic Weisbecker
2021-11-17T15:57:03Z

If a user wants to boot without any CPU in offloaded mode initially but
with the possibility to offload them later using cpusets, provide a way
to simply pass an empty "rcu_nocbs" kernel parameter which will enforce
the creation of dormant nocb kthreads.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
---
kernel/rcu/tree_nocb.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 1871f15b8472..3845f1885ffc 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -66,14 +66,16 @@ static bool rcu_nocb_is_setup;
static int __init rcu_nocb_setup(char *str)
{
alloc_bootmem_cpumask_var(&rcu_nocb_mask);
- if (cpulist_parse(str, rcu_nocb_mask)) {
- pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
- cpumask_setall(rcu_nocb_mask);
+ if (*str == '=') {
+ if (cpulist_parse(++str, rcu_nocb_mask)) {
+ pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
+ cpumask_setall(rcu_nocb_mask);
+ }
}
rcu_nocb_is_setup = true;
return 1;
}
-__setup("rcu_nocbs=", rcu_nocb_setup);
+__setup("rcu_nocbs", rcu_nocb_setup);

static int __init parse_rcu_nocb_poll(char *arg)
{
--
2.25.1