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Date: Sun, 30 Mar 2014 20:41:18 +0800
From: Fengguang Wu <fengguang.wu@intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>, LKML <linux-kernel@vger.kernel.org>,
        Stephane Eranian <eranian@google.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [reboot] WARNING: CPU: 0 PID: 112 at kernel/events/core.c:5655
 perf_swevent_add()
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This fix is not yet in linux-next, can anyone help merge it? Thanks!

On Tue, Mar 11, 2014 at 08:14:56PM +0800, Fengguang Wu wrote:
> Jiri,
> 
> It works, thank you!
> 
> Tested-by: Fengguang Wu <fengguang.wu@intel.com>
> 
> > ---
> > 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);
> >  }