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authorLiam R. Howlett <Liam.Howlett@oracle.com>2023-09-15 13:44:44 -0400
committerPeter Zijlstra <peterz@infradead.org>2023-09-19 10:48:04 +0200
commitcff9b2332ab762b7e0586c793c431a8f2ea4db04 (patch)
tree47b44aeadbfd968e701dea725ac1b026982f32e4 /kernel
parentce9ecca0238b140b88f43859b211c9fdfd8e5b70 (diff)
kernel/sched: Modify initial boot task idle setup
Initial booting is setting the task flag to idle (PF_IDLE) by the call path sched_init() -> init_idle(). Having the task idle and calling call_rcu() in kernel/rcu/tiny.c means that TIF_NEED_RESCHED will be set. Subsequent calls to any cond_resched() will enable IRQs, potentially earlier than the IRQ setup has completed. Recent changes have caused just this scenario and IRQs have been enabled early. This causes a warning later in start_kernel() as interrupts are enabled before they are fully set up. Fix this issue by setting the PF_IDLE flag later in the boot sequence. Although the boot task was marked as idle since (at least) d80e4fda576d, I am not sure that it is wrong to do so. The forced context-switch on idle task was introduced in the tiny_rcu update, so I'm going to claim this fixes 5f6130fa52ee. Fixes: 5f6130fa52ee ("tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-mm/CAMuHMdWpvpWoDa=Ox-do92czYRvkok6_x6pYUH+ZouMcJbXy+Q@mail.gmail.com/
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/core.c2
-rw-r--r--kernel/sched/idle.c1
2 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2299a5cfbfb9..802551e0009b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9269,7 +9269,7 @@ void __init init_idle(struct task_struct *idle, int cpu)
* PF_KTHREAD should already be set at this point; regardless, make it
* look like a proper per-CPU kthread.
*/
- idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY;
+ idle->flags |= PF_KTHREAD | PF_NO_SETAFFINITY;
kthread_set_per_cpu(idle, cpu);
#ifdef CONFIG_SMP
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 342f58a329f5..5007b25c5bc6 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -373,6 +373,7 @@ EXPORT_SYMBOL_GPL(play_idle_precise);
void cpu_startup_entry(enum cpuhp_state state)
{
+ current->flags |= PF_IDLE;
arch_cpu_idle_prepare();
cpuhp_online_idle(state);
while (1)