Re: [reboot] WARNING: CPU: 0 PID: 112 at kernel/events/core.c:5655 perf_swevent_add()

[Fengguang Wu]

Jiri,

It works, thank you!

Tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>

> ---
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 661951a..a53857e 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5423,6 +5423,8 @@ struct swevent_htable {
>  
>  	/* Recursion avoidance in each contexts */
>  	int				recursion[PERF_NR_CONTEXTS];
> +
> +	bool				offline;
>  };
>  
>  static DEFINE_PER_CPU(struct swevent_htable, swevent_htable);
> @@ -5669,8 +5671,10 @@ static int perf_swevent_add(struct perf_event *event, int flags)
>  	hwc->state = !(flags & PERF_EF_START);
>  
>  	head = find_swevent_head(swhash, event);
> -	if (WARN_ON_ONCE(!head))
> +	if (!head) {
> +		WARN_ON_ONCE(!swhash->offline);
>  		return -EINVAL;
> +	}
>  
>  	hlist_add_head_rcu(&event->hlist_entry, head);
>  
> @@ -7850,6 +7854,7 @@ static void perf_event_init_cpu(int cpu)
>  	struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
>  
>  	mutex_lock(&swhash->hlist_mutex);
> +	swhash->offline = false;
>  	if (swhash->hlist_refcount > 0) {
>  		struct swevent_hlist *hlist;
>  
> @@ -7907,6 +7912,7 @@ static void perf_event_exit_cpu(int cpu)
>  	perf_event_exit_cpu_context(cpu);
>  
>  	mutex_lock(&swhash->hlist_mutex);
> +	swhash->offline = true;
>  	swevent_hlist_release(swhash);
>  	mutex_unlock(&swhash->hlist_mutex);
>  }
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