Re: [PATCH 3/9] lib/ref_tracker: __ref_tracker_dir_print improve printing

[Andrzej Hajda <andrzej.hajda@xxxxxxxxx>]

On 17.02.2022 16:38, Eric Dumazet wrote:
> On Thu, Feb 17, 2022 at 6:05 AM Andrzej Hajda <andrzej.hajda@xxxxxxxxx> wrote:
> > To improve readibility of ref_tracker printing following changes
> > have been performed:
> > - 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.
> >
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > Reviewed-by: Chris Wilson <chris.p.wilson@xxxxxxxxx>
> > ---
> >   include/linux/ref_tracker.h | 15 ++++++++++++---
> >   lib/ref_tracker.c           | 28 ++++++++++++++++++++++------
> >   2 files changed, 34 insertions(+), 9 deletions(-)
> >
> > diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
> > index b9c968a716483..090230e5b485d 100644
> > --- a/include/linux/ref_tracker.h
> > +++ b/include/linux/ref_tracker.h
> > @@ -15,18 +15,26 @@ struct ref_tracker_dir {
> >          refcount_t              untracked;
> >          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
> > +#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)
> > +
> > +static inline void __ref_tracker_dir_init(struct ref_tracker_dir *dir,
> > +                                       unsigned int quarantine_count,
> > +                                       const char *name)
> >   {
> >          INIT_LIST_HEAD(&dir->list);
> >          INIT_LIST_HEAD(&dir->quarantine);
> >          spin_lock_init(&dir->lock);
> >          dir->quarantine_avail = quarantine_count;
> >          refcount_set(&dir->untracked, 1);
> > +       strlcpy(dir->name, name, sizeof(dir->name));
> >          stack_depot_init();
> >   }
> >
> > @@ -47,7 +55,8 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
> >   #else /* CONFIG_REF_TRACKER */
> >
> >   static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
> > -                                       unsigned int quarantine_count)
> > +                                       unsigned int quarantine_count,
> > +                                       ...)
> >   {
> >   }
> >
> > diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
> > index 0e9c7d2828ccb..943cff08110e3 100644
> > --- a/lib/ref_tracker.c
> > +++ b/lib/ref_tracker.c
> > @@ -1,4 +1,7 @@
> >   // SPDX-License-Identifier: GPL-2.0-or-later
> > +
> > +#define pr_fmt(fmt) "ref_tracker: " fmt
> > +
> >   #include <linux/export.h>
> >   #include <linux/list_sort.h>
> >   #include <linux/ref_tracker.h>
> > @@ -7,6 +10,7 @@
> >   #include <linux/stackdepot.h>
> >
> >   #define REF_TRACKER_STACK_ENTRIES 16
> > +#define STACK_BUF_SIZE 1024
>
> >   struct ref_tracker {
> >          struct list_head        head;   /* anchor into dir->list or dir->quarantine */
> > @@ -26,31 +30,43 @@ static int ref_tracker_cmp(void *priv, const struct list_head *a, const struct l
> >   void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
> >                             unsigned int display_limit)
> >   {
> > -       unsigned int i = 0, count = 0;
> > +       unsigned int i = 0, count = 0, total = 0;
> >          struct ref_tracker *tracker;
> >          depot_stack_handle_t stack;
> > +       char *sbuf;
> >
> >          lockdep_assert_held(&dir->lock);
> >
> >          if (list_empty(&dir->list))
> >                  return;
> >
> > +       sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT);
> > +
> > +       list_for_each_entry(tracker, &dir->list, head)
> > +               ++total;
> Another iteration over a potential long list.
>
> You can count the @skipped number in the following iteration just fine.

Skipped is already in 'count', but you are right with double looping> I 
can count total in the same loop,
just forgot to merge loops during code evolution.
Will be fixed.

Regards
Andrzej

> int skipped = 0;
>
> > +
> >          list_sort(NULL, &dir->list, ref_tracker_cmp);
> >
> >          list_for_each_entry(tracker, &dir->list, head) {
> > -               if (i++ >= display_limit)
> > -                       break;
> >                  if (!count++)
> >                          stack = tracker->alloc_stack_handle;
> >                  if (stack == tracker->alloc_stack_handle &&
> >                      !list_is_last(&tracker->head, &dir->list))
> >                          continue;
> > +               if (i++ >= display_limit)
>                              skipped++;
> > +                       continue;
> >
> > -               pr_err("leaked %d references.\n", count);
> > -               if (stack)
> > -                       stack_depot_print(stack);
> > +               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, count, total, sbuf);
> >                  count = 0;
> >          }
> > +       if (i > display_limit)
> > +               pr_err("%s@%pK skipped %d/%d reports with %d unique stacks.\n",
> > +                      dir->name, dir, count, total, i - display_limit);
> > +
> > +       kfree(sbuf);
> >   }
> >   EXPORT_SYMBOL(__ref_tracker_dir_print);
> >
> > --
> > 2.25.1