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

Eric Dumazet
2022-02-17T15:38:51Z

On Thu, Feb 17, 2022 at 6:05 AM Andrzej Hajda <andrzej.hajda@intel.com> 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@intel.com>
> Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>
> ---
> 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
>