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

[Eric Dumazet]

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.

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
>