linux/lib/ref_tracker.c
Eric Dumazet 4e66934eaa lib: add reference counting tracking infrastructure
It can be hard to track where references are taken and released.

In networking, we have annoying issues at device or netns dismantles,
and we had various proposals to ease root causing them.

This patch adds new infrastructure pairing refcount increases
and decreases. This will self document code, because programmers
will have to associate increments/decrements.

This is controled by CONFIG_REF_TRACKER which can be selected
by users of this feature.

This adds both cpu and memory costs, and thus should probably be
used with care.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-12-06 16:04:44 -08:00

141 lines
3.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/export.h>
#include <linux/ref_tracker.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/stackdepot.h>
#define REF_TRACKER_STACK_ENTRIES 16
struct ref_tracker {
struct list_head head; /* anchor into dir->list or dir->quarantine */
bool dead;
depot_stack_handle_t alloc_stack_handle;
depot_stack_handle_t free_stack_handle;
};
void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
{
struct ref_tracker *tracker, *n;
unsigned long flags;
bool leak = false;
spin_lock_irqsave(&dir->lock, flags);
list_for_each_entry_safe(tracker, n, &dir->quarantine, head) {
list_del(&tracker->head);
kfree(tracker);
dir->quarantine_avail++;
}
list_for_each_entry_safe(tracker, n, &dir->list, head) {
pr_err("leaked reference.\n");
if (tracker->alloc_stack_handle)
stack_depot_print(tracker->alloc_stack_handle);
leak = true;
list_del(&tracker->head);
kfree(tracker);
}
spin_unlock_irqrestore(&dir->lock, flags);
WARN_ON_ONCE(leak);
WARN_ON_ONCE(refcount_read(&dir->untracked) != 1);
}
EXPORT_SYMBOL(ref_tracker_dir_exit);
void ref_tracker_dir_print(struct ref_tracker_dir *dir,
unsigned int display_limit)
{
struct ref_tracker *tracker;
unsigned long flags;
unsigned int i = 0;
spin_lock_irqsave(&dir->lock, flags);
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;
}
}
spin_unlock_irqrestore(&dir->lock, flags);
}
EXPORT_SYMBOL(ref_tracker_dir_print);
int ref_tracker_alloc(struct ref_tracker_dir *dir,
struct ref_tracker **trackerp,
gfp_t gfp)
{
unsigned long entries[REF_TRACKER_STACK_ENTRIES];
struct ref_tracker *tracker;
unsigned int nr_entries;
unsigned long flags;
*trackerp = tracker = kzalloc(sizeof(*tracker), gfp | __GFP_NOFAIL);
if (unlikely(!tracker)) {
pr_err_once("memory allocation failure, unreliable refcount tracker.\n");
refcount_inc(&dir->untracked);
return -ENOMEM;
}
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
nr_entries = filter_irq_stacks(entries, nr_entries);
tracker->alloc_stack_handle = stack_depot_save(entries, nr_entries, gfp);
spin_lock_irqsave(&dir->lock, flags);
list_add(&tracker->head, &dir->list);
spin_unlock_irqrestore(&dir->lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(ref_tracker_alloc);
int ref_tracker_free(struct ref_tracker_dir *dir,
struct ref_tracker **trackerp)
{
unsigned long entries[REF_TRACKER_STACK_ENTRIES];
struct ref_tracker *tracker = *trackerp;
depot_stack_handle_t stack_handle;
unsigned int nr_entries;
unsigned long flags;
if (!tracker) {
refcount_dec(&dir->untracked);
return -EEXIST;
}
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
nr_entries = filter_irq_stacks(entries, nr_entries);
stack_handle = stack_depot_save(entries, nr_entries, GFP_ATOMIC);
spin_lock_irqsave(&dir->lock, flags);
if (tracker->dead) {
pr_err("reference already released.\n");
if (tracker->alloc_stack_handle) {
pr_err("allocated in:\n");
stack_depot_print(tracker->alloc_stack_handle);
}
if (tracker->free_stack_handle) {
pr_err("freed in:\n");
stack_depot_print(tracker->free_stack_handle);
}
spin_unlock_irqrestore(&dir->lock, flags);
WARN_ON_ONCE(1);
return -EINVAL;
}
tracker->dead = true;
tracker->free_stack_handle = stack_handle;
list_move_tail(&tracker->head, &dir->quarantine);
if (!dir->quarantine_avail) {
tracker = list_first_entry(&dir->quarantine, struct ref_tracker, head);
list_del(&tracker->head);
} else {
dir->quarantine_avail--;
tracker = NULL;
}
spin_unlock_irqrestore(&dir->lock, flags);
kfree(tracker);
return 0;
}
EXPORT_SYMBOL_GPL(ref_tracker_free);