sched,init: Fix DEBUG_PREEMPT vs early boot

Extend 8fb1215 ("init: Pin init task to the boot CPU, initially") to cover the new PF_NO_SETAFFINITY requirement. While there, move wait_for_completion(&kthreadd_done) into kernel_init() to make it absolutely clear it is the very first thing done by the init thread. Fixes: 570a752 ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed") Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Valentin Schneider <[email protected]> Tested-by: Valentin Schneider <[email protected]> Tested-by: Borislav Petkov <[email protected]> Link: https://lkml.kernel.org/r/[email protected]
tobetter · Jun 1, 2021 · 15faafc · 15faafc
1 parent 7b419f4
commit 15faafc
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Showing 2 changed files with 7 additions and 5 deletions.
diff --git a/init/main.c b/init/main.c
@@ -692,6 +692,7 @@ noinline void __ref rest_init(void)
 	 */
 	rcu_read_lock();
 	tsk = find_task_by_pid_ns(pid, &init_pid_ns);
+	tsk->flags |= PF_NO_SETAFFINITY;
 	set_cpus_allowed_ptr(tsk, cpumask_of(smp_processor_id()));
 	rcu_read_unlock();
 
@@ -1440,6 +1441,11 @@ static int __ref kernel_init(void *unused)
 {
 	int ret;
 
+	/*
+	 * Wait until kthreadd is all set-up.
+	 */
+	wait_for_completion(&kthreadd_done);
+
 	kernel_init_freeable();
 	/* need to finish all async __init code before freeing the memory */
 	async_synchronize_full();
@@ -1520,11 +1526,6 @@ void __init console_on_rootfs(void)
 
 static noinline void __init kernel_init_freeable(void)
 {
-	/*
-	 * Wait until kthreadd is all set-up.
-	 */
-	wait_for_completion(&kthreadd_done);
-
 	/* Now the scheduler is fully set up and can do blocking allocations */
 	gfp_allowed_mask = __GFP_BITS_MASK;
 

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
@@ -8862,6 +8862,7 @@ void __init sched_init_smp(void)
 	/* Move init over to a non-isolated CPU */
 	if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
 		BUG();
+	current->flags &= ~PF_NO_SETAFFINITY;
 	sched_init_granularity();
 
 	init_sched_rt_class();