Re: [PATCH linux-next v2] sched/core: Add WARN() to check overflow in migrate_disable()
From: Peter Zijlstra
Date: Thu Jul 04 2024 - 09:47:44 EST
On Wed, Jul 03, 2024 at 08:53:25PM +0800, xu.xin16@xxxxxxxxxx wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 8cc4975d6b2b..327010af6ce9 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2259,6 +2259,7 @@ void migrate_disable(void)
> struct task_struct *p = current;
>
> if (p->migration_disabled) {
> + WARN(p->migration_disabled == USHRT_MAX, "migration_disabled has encountered an overflow.");
> p->migration_disabled++;
> return;
> }
How about we do something like this?
---
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7a5ea8fc8abb..06a559532ed6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2237,6 +2237,12 @@ void migrate_disable(void)
if (p->migration_disabled) {
p->migration_disabled++;
+#ifdef CONFIG_DEBUG_PREEMPT
+ /*
+ * Warn about overflow half-way through the range.
+ */
+ WARN_ON_ONCE((s16)p->migration_disabled < 0);
+#endif
return;
}
@@ -2254,14 +2260,20 @@ void migrate_enable(void)
.flags = SCA_MIGRATE_ENABLE,
};
+#ifdef CONFIG_DEBUG_PREEMPT
+ /*
+ * Check both overflow from migrate_disable() and superfluous
+ * migrate_enable().
+ */
+ if (WARN_ON_ONCE((s16)p->migration_disabled <= 0))
+ return;
+#endif
+
if (p->migration_disabled > 1) {
p->migration_disabled--;
return;
}
- if (WARN_ON_ONCE(!p->migration_disabled))
- return;
-
/*
* Ensure stop_task runs either before or after this, and that
* __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().