Re: [PATCH 2.6.19-rc6] sched: cleanup output of show_state/show_task

[Chris Caputo <ccaputo@alt.net>]

On Mon, 27 Nov 2006, Andrew Morton wrote:
> On Sat, 25 Nov 2006 04:48:15 +0000 (GMT)
> Chris Caputo <ccaputo@alt.net> wrote:
> > This patch cleans up the output of show_state/task() (aka magic-sysrq-t) 
> > so that free stack space is printed as appropriate based on 
> > CONFIG_DEBUG_STACK_USAGE.
> > 
> > Also, without this patch the header is not aligned with the data and is 
> > thus confusing.  Free stack is labeled as pid, pid is labeled as father, 
> > and so on.
> > 
> > Signed-off-by: Chris Caputo <ccaputo@alt.net>
> > ---
> > 
> > diff -uprN a/kernel/sched.c b/kernel/sched.c
> > --- a/kernel/sched.c	2006-11-25 04:11:12.000000000 +0000
> > +++ b/kernel/sched.c	2006-11-25 04:13:07.000000000 +0000
> > @@ -4757,7 +4757,6 @@ static const char stat_nam[] = "RSDTtZX"
> >  static void show_task(struct task_struct *p)
> >  {
> >  	struct task_struct *relative;
> > -	unsigned long free = 0;
> >  	unsigned state;
> >  
> >  	state = p->state ? __ffs(p->state) + 1 : 0;
> > @@ -4779,10 +4778,10 @@ static void show_task(struct task_struct
> >  		unsigned long *n = end_of_stack(p);
> >  		while (!*n)
> >  			n++;
> > -		free = (unsigned long)n - (unsigned long)end_of_stack(p);
> > +		printk("%5lu ", (unsigned long)n - (unsigned long)end_of_stack(p));
> >  	}
> >  #endif
> > -	printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
> > +	printk("%5d %6d ", p->pid, p->parent->pid);
> 
> This will cause the output format to be dependent upon the setting of
> CONFIG_DEBUG_STACK_USAGE.  So any code which attempts to parse the output
> of this function will somehow need to work out whether or not the `free'
> field is present.
> 
> Which is why we still print out a zero if CONFIG_DEBUG_STACK_USAGE=n.

Ahh!

Should we make it so the header printed by show_state is aligned properly 
with the data?  If yes, please consider the below patch.

Chris

---
From: Chris Caputo <ccaputo@alt.net>
[PATCH 2.6.19-rc6] sched: correct output of show_state

At present show_state prints a header the does not match the output of 
show_task, as follows:

-
                                               sibling
  task             PC      pid father child younger older
init          S 00000000     0     1      0     2               (NOTLB)
-

This patch corrects the output of show_state so that the header is 
aligned with the data, ala:

-
                         free                        sibling
  task             PC    stack   pid father child younger older
init          S 00000000     0     1      0     2               (NOTLB)
-

Signed-off-by: Chris Caputo <ccaputo@alt.net>
---

--- a/kernel/sched.c	2006-11-27 08:40:56.000000000 +0000
+++ b/kernel/sched.c	2006-11-27 23:23:49.000000000 +0000
@@ -4810,12 +4810,12 @@ void show_state(void)
 
 #if (BITS_PER_LONG == 32)
 	printk("\n"
-	       "                                               sibling\n");
-	printk("  task             PC      pid father child younger older\n");
+	       "                         free                        sibling\n");
+	printk("  task             PC    stack   pid father child younger older\n");
 #else
 	printk("\n"
-	       "                                                       sibling\n");
-	printk("  task                 PC          pid father child younger older\n");
+	       "                                 free                        sibling\n");
+	printk("  task                 PC        stack   pid father child younger older\n");
 #endif
 	read_lock(&tasklist_lock);
 	do_each_thread(g, p) {