From 8e4b1d2bc198e34b48fc7cc3a3c5a2fcb269e271 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 31 Mar 2021 10:59:05 -0700 Subject: [PATCH] rcu: Invoke rcu_spawn_core_kthreads() from rcu_spawn_gp_kthread() Currently, rcu_spawn_core_kthreads() is invoked via an early_initcall(), which works, except that rcu_spawn_gp_kthread() is also invoked via an early_initcall() and rcu_spawn_core_kthreads() relies on adjustments to kthread_prio that are carried out by rcu_spawn_gp_kthread(). There is no guaranttee of ordering among early_initcall() handlers, and thus no guarantee that kthread_prio will be properly checked and range-limited at the time that rcu_spawn_core_kthreads() needs it. In most cases, this bug is harmless. After all, the only reason that rcu_spawn_gp_kthread() adjusts the value of kthread_prio is if the user specified a nonsensical value for this boot parameter, which experience indicates is rare. Nevertheless, a bug is a bug. This commit therefore causes the rcu_spawn_core_kthreads() function to be invoked directly from rcu_spawn_gp_kthread() after any needed adjustments to kthread_prio have been carried out. Fixes: 48d07c04b4cc ("rcu: Enable elimination of Tree-RCU softirq processing") Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 06f3de96997c..2532e584e95f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2889,7 +2889,6 @@ static int __init rcu_spawn_core_kthreads(void) "%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__); return 0; } -early_initcall(rcu_spawn_core_kthreads); /* * Handle any core-RCU processing required by a call_rcu() invocation. @@ -4450,6 +4449,7 @@ static int __init rcu_spawn_gp_kthread(void) wake_up_process(t); rcu_spawn_nocb_kthreads(); rcu_spawn_boost_kthreads(); + rcu_spawn_core_kthreads(); return 0; } early_initcall(rcu_spawn_gp_kthread);