Re: [Intel-gfx] [PATCH v4 02/10] lib/ref_tracker: __ref_tracker_dir_print improve printing

[Andrzej Hajda]

On 20.03.2023 00:11, Andi Shyti wrote:
> Hi Andrzej,
>
> looks good, few comments below,
>
> On Mon, Mar 06, 2023 at 05:31:58PM +0100, Andrzej Hajda wrote:
> > To improve readability of ref_tracker printing following changes
> > have been performed:
> > - reports are printed per stack_handle - log is more compact,
> > - added display name for ref_tracker_dir,
> > - stack trace is printed indented, in the same printk call,
> > - total number of references is printed every time,
> > - print info about dropped references.
>
> nit: I think you can do better with the log :)
>
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > ---
> >   include/linux/ref_tracker.h | 15 ++++++--
> >   lib/ref_tracker.c           | 90 +++++++++++++++++++++++++++++++++++++++------
> >   2 files changed, 91 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
> > index 3e9e9df2a41f5f..a2cf1f6309adb2 100644
> > --- a/include/linux/ref_tracker.h
> > +++ b/include/linux/ref_tracker.h
> > @@ -17,12 +17,19 @@ struct ref_tracker_dir {
> >   	bool			dead;
> >   	struct list_head	list; /* List of active trackers */
> >   	struct list_head	quarantine; /* List of dead trackers */
> > +	char			name[32];
> >   #endif
> >   };
> >   
> >   #ifdef CONFIG_REF_TRACKER
> > -static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
> > -					unsigned int quarantine_count)
> > +
> > +// Temporary allow two and three arguments, until consumers are converted
>
> I thought only Linus was allowed to use '//' :)
>
> > +#define ref_tracker_dir_init(_d, _q, args...) _ref_tracker_dir_init(_d, _q, ##args, #_d)
> > +#define _ref_tracker_dir_init(_d, _q, _n, ...) __ref_tracker_dir_init(_d, _q, _n)
>
> [...]
>
> > +void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
> > +			   unsigned int display_limit)
> > +{
> > +	struct ref_tracker_dir_stats *stats;
> > +	unsigned int i = 0, skipped;
> > +	depot_stack_handle_t stack;
> > +	char *sbuf;
> > +
> > +	lockdep_assert_held(&dir->lock);
> > +
> > +	if (list_empty(&dir->list))
> > +		return;
> > +
> > +	stats = ref_tracker_get_stats(dir, display_limit);
> > +	if (IS_ERR(stats)) {
> > +		pr_err("%s@%pK: couldn't get stats, error %pe\n",
> > +		       dir->name, dir, stats);
> > +		return;
> >   	}
> > +
> > +	sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
> > +
> > +	for (i = 0, skipped = stats->total; i < stats->count; ++i) {
> > +		stack = stats->stacks[i].stack_handle;
> > +		if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
> > +			sbuf[0] = 0;
> > +		pr_err("%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
> > +		       stats->stacks[i].count, stats->total, sbuf);
>
> what if sbuf is NULL?

Then "(NULL)" will be printed, I suspect it will occur only on very rare 
occasions.

> > +		skipped -= stats->stacks[i].count;
> > +	}
> > +
> > +	if (skipped)
>
> is skipped used to double check whether stats->count is equal to
> all the stacks[].conunts? What are the cases when skipped is > 0?

There is display_limit parameter, so the function prints up to 
display_limit reports, and brief summary on remaining ones - the skipped 
ones.

Regards
Andrzej


> Andi
>
> > +		pr_err("%s@%pK skipped reports about %d/%d users.\n",
> > +		       dir->name, dir, skipped, stats->total);
> > +
> > +	kfree(sbuf);
> > +
> > +	kfree(stats);
> >   }
> >   EXPORT_SYMBOL(__ref_tracker_dir_print);
> >   
> >
> > --
> > 2.34.1