Re: [PATCH] tracing/ftrace: fix a memory leak in stat tracing

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, Jan 06, 2009 at 03:43:09PM -0500, Steven Rostedt wrote:
> 
> Thanks Frederic!
> 
> I'll just add an Impact line to this and push it off to Ingo.


Thanks!
 
> The impact line will simply be:
> 
> 	Impact: fix memory leak


Yes I wanted to put one similar to yours but I thought it duplicated
the subject line. But you're right I guess that could help those who will grep
git-log on Impact lines.


> -- Steve
> 
> On Tue, 6 Jan 2009, Frederic Weisbecker wrote:
> 
> > This patch fixes a memory leak inside reset_stat_list(). The freeing
> > loop iterated only once.
> > 
> > Also turn the stat_list into a simple struct list_head, which
> > simplify the code and avoid an unused static pointer.
> > 
> > Reported-by: Steven Rostedt <rostedt@goodmis.org>
> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> > ---
> > diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
> > index 6f194a3..4cb4ff2 100644
> > --- a/kernel/trace/trace_stat.c
> > +++ b/kernel/trace/trace_stat.c
> > @@ -21,7 +21,7 @@ struct trace_stat_list {
> >  	void *stat;
> >  };
> >  
> > -static struct trace_stat_list stat_list;
> > +static LIST_HEAD(stat_list);
> >  
> >  /*
> >   * This is a copy of the current tracer to avoid racy
> > @@ -39,22 +39,12 @@ static DEFINE_MUTEX(stat_list_mutex);
> >  
> >  static void reset_stat_list(void)
> >  {
> > -	struct trace_stat_list *node;
> > -	struct list_head *next;
> > +	struct trace_stat_list *node, *next;
> >  
> > -	if (list_empty(&stat_list.list))
> > -		return;
> > -
> > -	node = list_entry(stat_list.list.next, struct trace_stat_list, list);
> > -	next = node->list.next;
> > -
> > -	while (&node->list != next) {
> > +	list_for_each_entry_safe(node, next, &stat_list, list)
> >  		kfree(node);
> > -		node = list_entry(next, struct trace_stat_list, list);
> > -	}
> > -	kfree(node);
> >  
> > -	INIT_LIST_HEAD(&stat_list.list);
> > +	INIT_LIST_HEAD(&stat_list);
> >  }
> >  
> >  void init_tracer_stat(struct tracer *trace)
> > @@ -107,7 +97,7 @@ static int stat_seq_init(void)
> >  	}
> >  
> >  	INIT_LIST_HEAD(&new_entry->list);
> > -	list_add(&new_entry->list, &stat_list.list);
> > +	list_add(&new_entry->list, &stat_list);
> >  	new_entry->stat = current_tracer.stat_start();
> >  
> >  	prev_stat = new_entry->stat;
> > @@ -130,7 +120,7 @@ static int stat_seq_init(void)
> >  		if (!new_entry->stat)
> >  			break;
> >  
> > -		list_for_each_entry(iter_entry, &stat_list.list, list) {
> > +		list_for_each_entry(iter_entry, &stat_list, list) {
> >  			/* Insertion with a descendent sorting */
> >  			if (current_tracer.stat_cmp(new_entry->stat,
> >  						iter_entry->stat) > 0) {
> > @@ -141,7 +131,7 @@ static int stat_seq_init(void)
> >  
> >  			/* The current smaller value */
> >  			} else if (list_is_last(&iter_entry->list,
> > -						&stat_list.list)) {
> > +						&stat_list)) {
> >  				list_add(&new_entry->list, &iter_entry->list);
> >  				break;
> >  			}
> > @@ -162,7 +152,7 @@ exit_free_list:
> >  
> >  static void *stat_seq_start(struct seq_file *s, loff_t *pos)
> >  {
> > -	struct trace_stat_list *l = (struct trace_stat_list *)s->private;
> > +	struct list_head *l = (struct list_head *)s->private;
> >  
> >  	/* Prevent from tracer switch or stat_list modification */
> >  	mutex_lock(&stat_list_mutex);
> > @@ -171,14 +161,14 @@ static void *stat_seq_start(struct seq_file *s, loff_t *pos)
> >  	if (!*pos && current_tracer.stat_headers)
> >  		current_tracer.stat_headers(s);
> >  
> > -	return seq_list_start(&l->list, *pos);
> > +	return seq_list_start(l, *pos);
> >  }
> >  
> >  static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
> >  {
> > -	struct trace_stat_list *l = (struct trace_stat_list *)s->private;
> > +	struct list_head *l = (struct list_head *)s->private;
> >  
> > -	return seq_list_next(p, &l->list, pos);
> > +	return seq_list_next(p, l, pos);
> >  }
> >  
> >  static void stat_seq_stop(struct seq_file *m, void *p)
> > @@ -188,8 +178,10 @@ static void stat_seq_stop(struct seq_file *m, void *p)
> >  
> >  static int stat_seq_show(struct seq_file *s, void *v)
> >  {
> > -	struct trace_stat_list *l = list_entry(v, struct trace_stat_list, list);
> > -	return current_tracer.stat_show(s, l->stat);
> > +	struct trace_stat_list *entry =
> > +		list_entry(v, struct trace_stat_list, list);
> > +
> > +	return current_tracer.stat_show(s, entry->stat);
> >  }
> >  
> >  static const struct seq_operations trace_stat_seq_ops = {
> > @@ -237,7 +229,6 @@ static int __init tracing_stat_init(void)
> >  	struct dentry *d_tracing;
> >  	struct dentry *entry;
> >  
> > -	INIT_LIST_HEAD(&stat_list.list);
> >  	d_tracing = tracing_init_dentry();
> >  
> >  	entry = debugfs_create_file("trace_stat", 0444, d_tracing,
> > -- 
> > 1.6.0.4
> > 
> > 
> > 
> >