On 22.02.2022 01:08, Eric Dumazet wrote:
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 ?
I though also about it, but decided to left this change to another patch
as the change can be substantial and could open another discussion.
I am not sure what you mean by 'caller' but it could be even external
user of the API:
1. alloc data for ref_tracker_dir_stats.
2. take locks, if necessary.
3. gather stats (ref_tracker_get_stats) atomically.
4. release taken locks.
5. print stats.
This way, allocation and printing would happen outside locks.
+ 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.
The problem is that in my scenario it can be called under spinlock, this
is why I want almost everywhere non-sleeping allocations.
This is debugging infra, it would be sad if we give up at this point,
after storing MB of traces :)
My approach was to avoid allocations if the system is short on memory -
better to keep it alive, and we still get the report, just without
stacktraces, one can print full stats later (for example via sysfs, or
trigger to dmesg) - big chances that the bug will be still there.
If you think that is no-go, alternatives I see:
- go back to GFP_ATOMIC,
- print stack directly, without using stack_depot_snprint,
- pre-allocate buffer.
Regards
Andrzej
+
+ 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
