Re: /proc/timer_list and weird behavior with dropbear

[Nathan Zimmer]

On Fri, Jul 19, 2013 at 03:33:24PM -0500, Nathan Zimmer wrote:
> On Fri, Jul 19, 2013 at 07:03:54PM +0200, Holger Hans Peter Freyther wrote:
> > On Fri, Jul 19, 2013 at 10:45:15AM -0500, Nathan Zimmer wrote:
> > 
> > > I hadn't noticed anything.
> > > Let me try your program and see what I may have missed.
> > 
> > Hi,
> > 
> > I neither know the semantics of the timer_list nor how to use
> > seq_file correctly. What happens is that timer_list_next will only
> > be called once. This means that iter->cpu will never be increased.
> > 
> > This just moves to the next CPU when stop is called (e.g. nothing
> > was added once the print_tickdevice was printed). Do you think
> > this could be correct?
> > 
> > 
> > 
> > diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
> > index 3bdf283..8d36a3d 100644
> > --- a/kernel/time/timer_list.c
> > +++ b/kernel/time/timer_list.c
> > @@ -327,8 +327,10 @@ static void *timer_list_next(struct seq_file *file, void *v, loff_t *offset)
> >  	return timer_list_start(file, offset);
> >  }
> >  
> > -static void timer_list_stop(struct seq_file *seq, void *v)
> > +static void timer_list_stop(struct seq_file *file, void *v)
> >  {
> > +	struct timer_list_iter *iter = file->private;
> > +	iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
> >  }
> >  
> >  static const struct seq_operations timer_list_sops = {
> 
> 
> I think this would be an acceptable fix.
> It work file locally.  Could you check it out to see if it behaves?
> 
> Nate

Forgot the patch last time.
Sorry

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 3bdf283..a3620ec 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -305,24 +305,26 @@ static void *timer_list_start(struct seq_file *file, loff_t *offset)
 	if (!*offset) {
 		iter->cpu = -1;
 		iter->now = ktime_to_ns(ktime_get());
-	} else if (iter->cpu >= nr_cpu_ids) {
+	} else {
+		iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
+		if (iter->cpu >= nr_cpu_ids) {
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
-		if (!iter->second_pass) {
-			iter->cpu = -1;
-			iter->second_pass = true;
-		} else
-			return NULL;
+			if (!iter->second_pass) {
+				iter->cpu = -1;
+				iter->second_pass = true;
+			} else
+				return NULL;
 #else
-		return NULL;
+			return NULL;
 #endif
+		}
 	}
+
 	return iter;
 }
 
 static void *timer_list_next(struct seq_file *file, void *v, loff_t *offset)
 {
-	struct timer_list_iter *iter = file->private;
-	iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
 	++*offset;
 	return timer_list_start(file, offset);
 }