Re: [PATCH v3 05/11] lib/ref_tracker: __ref_tracker_dir_print improve printing
From: Eric Dumazet
Date: Mon Feb 21 2022 - 19:08:29 EST
On Mon, Feb 21, 2022 at 3:26 PM Andrzej Hajda <andrzej.hajda@xxxxxxxxx> wrote:
>
> To improve readibility of ref_tracker printing following changes
readability
> 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.
>
> 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 3e9e9df2a41f5..a2cf1f6309adb 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
> +#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);
> @@ -31,6 +38,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
> dir->dead = false;
> refcount_set(&dir->untracked, 1);
> refcount_set(&dir->no_tracker, 1);
> + strlcpy(dir->name, name, sizeof(dir->name));
> stack_depot_init();
> }
>
> @@ -51,7 +59,8 @@ 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 5e9f90bbf771b..ab1253fde244e 100644
> --- a/lib/ref_tracker.c
> +++ b/lib/ref_tracker.c
> @@ -1,11 +1,16 @@
> // 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>
> #include <linux/slab.h>
> #include <linux/stacktrace.h>
> #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 */
> @@ -14,24 +19,87 @@ struct ref_tracker {
> depot_stack_handle_t free_stack_handle;
> };
>
> -void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
> - unsigned int display_limit)
> +struct ref_tracker_dir_stats {
> + int total;
> + int count;
> + struct {
> + depot_stack_handle_t stack_handle;
> + unsigned int count;
> + } stacks[];
> +};
> +
> +static struct ref_tracker_dir_stats *
> +ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
> {
> + struct ref_tracker_dir_stats *stats;
> struct ref_tracker *tracker;
> - unsigned int i = 0;
>
> - lockdep_assert_held(&dir->lock);
> + stats = kmalloc(struct_size(stats, stacks, limit),
> + GFP_NOWAIT | __GFP_NOWARN);
I would be more comfortable if the allocation was done by the caller,
possibly using GFP_KERNEL and evenutally kvmalloc(),
instead of under dir->lock ?
> + if (!stats)
> + return ERR_PTR(-ENOMEM);
> + stats->total = 0;
> + stats->count = 0;
>
> list_for_each_entry(tracker, &dir->list, head) {
> - if (i < display_limit) {
> - pr_err("leaked reference.\n");
> - if (tracker->alloc_stack_handle)
> - stack_depot_print(tracker->alloc_stack_handle);
> - i++;
> - } else {
> - break;
> + depot_stack_handle_t stack = tracker->alloc_stack_handle;
> + int i;
> +
> + ++stats->total;
> + for (i = 0; i < stats->count; ++i)
> + if (stats->stacks[i].stack_handle == stack)
> + break;
> + if (i >= limit)
> + continue;
> + if (i >= stats->count) {
> + stats->stacks[i].stack_handle = stack;
> + stats->stacks[i].count = 0;
> + ++stats->count;
> }
> + ++stats->stacks[i].count;
> + }
> +
> + return stats;
> +}
> +
> +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);
Same remark. These allocations are most probably going to happen from process
context, I think GFP_KERNEL is more robust.
This is debugging infra, it would be sad if we give up at this point,
after storing MB of traces :)
> +
> + 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);
> + skipped -= stats->stacks[i].count;
> + }
> +
> + if (skipped)
> + 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);
>
> --
> 2.25.1
>