| From 88f31cd38603f267facce8b2fa5535751b5f36d8 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 31 Mar 2021 10:59:05 -0700 |
| Subject: rcu: Invoke rcu_spawn_core_kthreads() from rcu_spawn_gp_kthread() |
| |
| From: Paul E. McKenney <paulmck@kernel.org> |
| |
| [ Upstream commit 8e4b1d2bc198e34b48fc7cc3a3c5a2fcb269e271 ] |
| |
| 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 <paulmck@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 61e250cdd7c9..45b60e997461 100644 |
| --- a/kernel/rcu/tree.c |
| +++ b/kernel/rcu/tree.c |
| @@ -2837,7 +2837,6 @@ 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. |
| @@ -4273,6 +4272,7 @@ 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); |
| -- |
| 2.30.2 |
| |
