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Subject[PATCH v6 03/16] locking/lockdep: Make zap_class() remove all matching lock order entries
Date
Make sure that all lock order entries that refer to a class are removed
from the list_entries[] array when a kernel module is unloaded.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
include/linux/lockdep.h | 1 +
kernel/locking/lockdep.c | 19 +++++++++++++------
2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c5335df2372f..71caa1118f4c 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -178,6 +178,7 @@ static inline void lockdep_copy_map(struct lockdep_map *to,
struct lock_list {
struct list_head entry;
struct lock_class *class;
+ struct lock_class *links_to;
struct stack_trace trace;
int distance;

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7a7c2d7b01c2..e52ce8745cba 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -859,7 +859,8 @@ static struct lock_list *alloc_list_entry(void)
/*
* Add a new dependency to the head of the list:
*/
-static int add_lock_to_list(struct lock_class *this, struct list_head *head,
+static int add_lock_to_list(struct lock_class *this,
+ struct lock_class *links_to, struct list_head *head,
unsigned long ip, int distance,
struct stack_trace *trace)
{
@@ -873,6 +874,7 @@ static int add_lock_to_list(struct lock_class *this, struct list_head *head,
return 0;

entry->class = this;
+ entry->links_to = links_to;
entry->distance = distance;
entry->trace = *trace;
/*
@@ -1918,14 +1920,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
* Ok, all validations passed, add the new lock
* to the previous lock's dependency list:
*/
- ret = add_lock_to_list(hlock_class(next),
+ ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
&hlock_class(prev)->locks_after,
next->acquire_ip, distance, trace);

if (!ret)
return 0;

- ret = add_lock_to_list(hlock_class(prev),
+ ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
&hlock_class(next)->locks_before,
next->acquire_ip, distance, trace);
if (!ret)
@@ -4119,15 +4121,20 @@ void lockdep_reset(void)
*/
static void zap_class(struct lock_class *class)
{
+ struct lock_list *entry;
int i;

/*
* Remove all dependencies this lock is
* involved in:
*/
- for (i = 0; i < nr_list_entries; i++) {
- if (list_entries[i].class == class)
- list_del_rcu(&list_entries[i].entry);
+ for (i = 0, entry = list_entries; i < nr_list_entries; i++, entry++) {
+ if (entry->class != class && entry->links_to != class)
+ continue;
+ list_del_rcu(&entry->entry);
+ /* Clear .class and .links_to to avoid double removal. */
+ WRITE_ONCE(entry->class, NULL);
+ WRITE_ONCE(entry->links_to, NULL);
}
/*
* Unhash the class and remove it from the all_lock_classes list:
--
2.20.1.97.g81188d93c3-goog
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