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A single commit for debug objects which fixes a pile of potential data

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races detected by KCSAN.
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Merge tag 'core-debugobjects-2020-01-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull debugobjects update from Thomas Gleixner:
 "A single commit for debug objects which fixes a pile of potential data
  races detected by KCSAN"

* tag 'core-debugobjects-2020-01-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobjects: Fix various data races
This commit is contained in:
Linus Torvalds 2020-01-27 16:45:58 -08:00
parent b11c89a158 35fd7a637c
commit 534b0a8b67
1 changed files with 25 additions and 21 deletions
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46
lib/debugobjects.c
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@ -132,14 +132,18 @@ static void fill_pool(void)
struct debug_obj *obj;
unsigned long flags;
if (likely(obj_pool_free >= debug_objects_pool_min_level))
if (likely(READ_ONCE(obj_pool_free) >= debug_objects_pool_min_level))
return;
/*
* Reuse objs from the global free list; they will be reinitialized
* when allocating.
*
* Both obj_nr_tofree and obj_pool_free are checked locklessly; the
* READ_ONCE()s pair with the WRITE_ONCE()s in pool_lock critical
* sections.
*/
while (obj_nr_tofree && (obj_pool_free < obj_pool_min_free)) {
while (READ_ONCE(obj_nr_tofree) && (READ_ONCE(obj_pool_free) < obj_pool_min_free)) {
raw_spin_lock_irqsave(&pool_lock, flags);
/*
* Recheck with the lock held as the worker thread might have
@ -148,9 +152,9 @@ static void fill_pool(void)
while (obj_nr_tofree && (obj_pool_free < obj_pool_min_free)) {
obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
hlist_del(&obj->node);
obj_nr_tofree--;
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree - 1);
hlist_add_head(&obj->node, &obj_pool);
obj_pool_free++;
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
}
@ -158,7 +162,7 @@ static void fill_pool(void)
if (unlikely(!obj_cache))
return;
while (obj_pool_free < debug_objects_pool_min_level) {
while (READ_ONCE(obj_pool_free) < debug_objects_pool_min_level) {
struct debug_obj *new[ODEBUG_BATCH_SIZE];
int cnt;
@ -174,7 +178,7 @@ static void fill_pool(void)
while (cnt) {
hlist_add_head(&new[--cnt]->node, &obj_pool);
debug_objects_allocated++;
obj_pool_free++;
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
}
@ -236,7 +240,7 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
obj = __alloc_object(&obj_pool);
if (obj) {
obj_pool_used++;
obj_pool_free--;
WRITE_ONCE(obj_pool_free, obj_pool_free - 1);
/*
* Looking ahead, allocate one batch of debug objects and
@ -255,7 +259,7 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
&percpu_pool->free_objs);
percpu_pool->obj_free++;
obj_pool_used++;
obj_pool_free--;
WRITE_ONCE(obj_pool_free, obj_pool_free - 1);
}
}
@ -309,8 +313,8 @@ static void free_obj_work(struct work_struct *work)
obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
hlist_del(&obj->node);
hlist_add_head(&obj->node, &obj_pool);
obj_pool_free++;
obj_nr_tofree--;
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree - 1);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
return;
@ -324,7 +328,7 @@ free_objs:
if (obj_nr_tofree) {
hlist_move_list(&obj_to_free, &tofree);
debug_objects_freed += obj_nr_tofree;
obj_nr_tofree = 0;
WRITE_ONCE(obj_nr_tofree, 0);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
@ -375,10 +379,10 @@ free_to_obj_pool:
obj_pool_used--;
if (work) {
obj_nr_tofree++;
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree + 1);
hlist_add_head(&obj->node, &obj_to_free);
if (lookahead_count) {
obj_nr_tofree += lookahead_count;
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree + lookahead_count);
obj_pool_used -= lookahead_count;
while (lookahead_count) {
hlist_add_head(&objs[--lookahead_count]->node,
@ -396,15 +400,15 @@ free_to_obj_pool:
for (i = 0; i < ODEBUG_BATCH_SIZE; i++) {
obj = __alloc_object(&obj_pool);
hlist_add_head(&obj->node, &obj_to_free);
obj_pool_free--;
obj_nr_tofree++;
WRITE_ONCE(obj_pool_free, obj_pool_free - 1);
WRITE_ONCE(obj_nr_tofree, obj_nr_tofree + 1);
}
}
} else {
obj_pool_free++;
WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
hlist_add_head(&obj->node, &obj_pool);
if (lookahead_count) {
obj_pool_free += lookahead_count;
WRITE_ONCE(obj_pool_free, obj_pool_free + lookahead_count);
obj_pool_used -= lookahead_count;
while (lookahead_count) {
hlist_add_head(&objs[--lookahead_count]->node,
@ -423,7 +427,7 @@ free_to_obj_pool:
static void free_object(struct debug_obj *obj)
{
__free_object(obj);
if (!obj_freeing && obj_nr_tofree) {
if (!READ_ONCE(obj_freeing) && READ_ONCE(obj_nr_tofree)) {
WRITE_ONCE(obj_freeing, true);
schedule_delayed_work(&debug_obj_work, ODEBUG_FREE_WORK_DELAY);
}
@ -982,7 +986,7 @@ repeat:
debug_objects_maxchecked = objs_checked;
/* Schedule work to actually kmem_cache_free() objects */
if (!obj_freeing && obj_nr_tofree) {
if (!READ_ONCE(obj_freeing) && READ_ONCE(obj_nr_tofree)) {
WRITE_ONCE(obj_freeing, true);
schedule_delayed_work(&debug_obj_work, ODEBUG_FREE_WORK_DELAY);
}
@ -1008,12 +1012,12 @@ static int debug_stats_show(struct seq_file *m, void *v)
seq_printf(m, "max_checked :%d\n", debug_objects_maxchecked);
seq_printf(m, "warnings :%d\n", debug_objects_warnings);
seq_printf(m, "fixups :%d\n", debug_objects_fixups);
seq_printf(m, "pool_free :%d\n", obj_pool_free + obj_percpu_free);
seq_printf(m, "pool_free :%d\n", READ_ONCE(obj_pool_free) + obj_percpu_free);
seq_printf(m, "pool_pcp_free :%d\n", obj_percpu_free);
seq_printf(m, "pool_min_free :%d\n", obj_pool_min_free);
seq_printf(m, "pool_used :%d\n", obj_pool_used - obj_percpu_free);
seq_printf(m, "pool_max_used :%d\n", obj_pool_max_used);
seq_printf(m, "on_free_list :%d\n", obj_nr_tofree);
seq_printf(m, "on_free_list :%d\n", READ_ONCE(obj_nr_tofree));
seq_printf(m, "objs_allocated:%d\n", debug_objects_allocated);
seq_printf(m, "objs_freed :%d\n", debug_objects_freed);
return 0;