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authorEric Dumazet <edumazet@google.com>2021-12-04 20:21:55 -0800
committerJakub Kicinski <kuba@kernel.org>2021-12-06 16:04:44 -0800
commit4e66934eaadc83b27ada8d42b60894018f3bfabf (patch)
treefc56c9432018c4128c6462cc5f970bd2212aab9d /lib
parentce83278f313ce65a9bbd780a3e07fa3f62d82525 (diff)
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig5
-rw-r--r--lib/Makefile2
-rw-r--r--lib/ref_tracker.c140
3 files changed, 147 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 5e7165e6a346..655b0e43f260 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -680,6 +680,11 @@ config STACK_HASH_ORDER
Select the hash size as a power of 2 for the stackdepot hash table.
Choose a lower value to reduce the memory impact.
+config REF_TRACKER
+ bool
+ depends on STACKTRACE_SUPPORT
+ select STACKDEPOT
+
config SBITMAP
bool
diff --git a/lib/Makefile b/lib/Makefile
index 364c23f15578..c1fd9243ddb9 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -270,6 +270,8 @@ obj-$(CONFIG_STACKDEPOT) += stackdepot.o
KASAN_SANITIZE_stackdepot.o := n
KCOV_INSTRUMENT_stackdepot.o := n
+obj-$(CONFIG_REF_TRACKER) += ref_tracker.o
+
libfdt_files = fdt.o fdt_ro.o fdt_wip.o fdt_rw.o fdt_sw.o fdt_strerror.o \
fdt_empty_tree.o fdt_addresses.o
$(foreach file, $(libfdt_files), \
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
new file mode 100644
index 000000000000..0ae2e66dcf0f
--- /dev/null
+++ b/lib/ref_tracker.c
@@ -0,0 +1,140 @@
+// 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);