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kmemleak: avoid RCU stalls when freeing metadata for per-CPU pointers 

On systems with large number of CPUs, the following soft lockup splat
might sometimes happen:

[ 2656.001617] watchdog: BUG: soft lockup - CPU#364 stuck for 21s! [ksoftirqd/364:2206]
  :
[ 2656.141194] RIP: 0010:_raw_spin_unlock_irqrestore+0x3d/0x70
  :
 2656.241214] Call Trace:
[ 2656.243971]  <IRQ>
[ 2656.246237]  ? show_trace_log_lvl+0x1c4/0x2df
[ 2656.251152]  ? show_trace_log_lvl+0x1c4/0x2df
[ 2656.256066]  ? kmemleak_free_percpu+0x11f/0x1f0
[ 2656.261173]  ? watchdog_timer_fn+0x379/0x470
[ 2656.265984]  ? __pfx_watchdog_timer_fn+0x10/0x10
[ 2656.271179]  ? __hrtimer_run_queues+0x5f3/0xd00
[ 2656.276283]  ? __pfx___hrtimer_run_queues+0x10/0x10
[ 2656.281783]  ? ktime_get_update_offsets_now+0x95/0x2c0
[ 2656.287573]  ? ktime_get_update_offsets_now+0xdd/0x2c0
[ 2656.293380]  ? hrtimer_interrupt+0x2e9/0x780
[ 2656.298221]  ? __sysvec_apic_timer_interrupt+0x184/0x640
[ 2656.304211]  ? sysvec_apic_timer_interrupt+0x8e/0xc0
[ 2656.309807]  </IRQ>
[ 2656.312169]  <TASK>
[ 2656.326110]  kmemleak_free_percpu+0x11f/0x1f0
[ 2656.331015]  free_percpu.part.0+0x1b/0xe70
[ 2656.335635]  free_vfsmnt+0xb9/0x100
[ 2656.339567]  rcu_do_batch+0x3c8/0xe30
[ 2656.363693]  rcu_core+0x3de/0x5a0
[ 2656.367433]  __do_softirq+0x2d0/0x9a8
[ 2656.381119]  run_ksoftirqd+0x36/0x60
[ 2656.385145]  smpboot_thread_fn+0x556/0x910
[ 2656.394971]  kthread+0x2a4/0x350
[ 2656.402826]  ret_from_fork+0x29/0x50
[ 2656.406861]  </TASK>

The issue is caused by kmemleak registering each per_cpu_ptr()
corresponding to the __percpu pointer.  This is unnecessary since such
individual per-CPU pointers are not tracked anyway.  Create a new
object_percpu_tree_root rbtree that stores a single __percpu pointer
together with an OBJECT_PERCPU flag for the kmemleak metadata.  Scanning
needs to be done for all per_cpu_ptr() pointers with a cond_resched()
between each CPU iteration to avoid RCU stalls.

[catalin.marinas@arm.com: update comment]
  Link: https://lkml.kernel.org/r/20231206114414.2085824-1-catalin.marinas@arm.com
  Link: https://lore.kernel.org/r/20231127194153.289626-1-longman@redhat.comLink: https://lkml.kernel.org/r/20231201190829.825856-1-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Waiman Long <longman@redhat.com>
Closes: https://lore.kernel.org/r/20231127194153.289626-1-longman@redhat.com
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Catalin Marinas 2023-12-01 19:08:29 +00:00 committed by Andrew Morton
parent f67f8d4a8c
commit 39042079a0
1 changed files with 97 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

178
mm/kmemleak.c
View File

@ -14,17 +14,15 @@
* The following locks and mutexes are used by kmemleak:
*
* - kmemleak_lock (raw_spinlock_t): protects the object_list as well as
* del_state modifications and accesses to the object_tree_root (or
* object_phys_tree_root). The object_list is the main list holding the
* metadata (struct kmemleak_object) for the allocated memory blocks.
* The object_tree_root and object_phys_tree_root are red
* black trees used to look-up metadata based on a pointer to the
* corresponding memory block. The object_phys_tree_root is for objects
* allocated with physical address. The kmemleak_object structures are
* added to the object_list and object_tree_root (or object_phys_tree_root)
* in the create_object() function called from the kmemleak_alloc() (or
* kmemleak_alloc_phys()) callback and removed in delete_object() called from
* the kmemleak_free() callback
* del_state modifications and accesses to the object trees
* (object_tree_root, object_phys_tree_root, object_percpu_tree_root). The
* object_list is the main list holding the metadata (struct
* kmemleak_object) for the allocated memory blocks. The object trees are
* red black trees used to look-up metadata based on a pointer to the
* corresponding memory block. The kmemleak_object structures are added to
* the object_list and the object tree root in the create_object() function
* called from the kmemleak_alloc{,_phys,_percpu}() callback and removed in
* delete_object() called from the kmemleak_free{,_phys,_percpu}() callback
* - kmemleak_object.lock (raw_spinlock_t): protects a kmemleak_object.
* Accesses to the metadata (e.g. count) are protected by this lock. Note
* that some members of this structure may be protected by other means
@ -178,6 +176,8 @@ struct kmemleak_object {
#define OBJECT_FULL_SCAN (1 << 3)
/* flag set for object allocated with physical address */
#define OBJECT_PHYS (1 << 4)
/* flag set for per-CPU pointers */
#define OBJECT_PERCPU (1 << 5)
/* set when __remove_object() called */
#define DELSTATE_REMOVED (1 << 0)
@ -206,6 +206,8 @@ static LIST_HEAD(mem_pool_free_list);
static struct rb_root object_tree_root = RB_ROOT;
/* search tree for object (with OBJECT_PHYS flag) boundaries */
static struct rb_root object_phys_tree_root = RB_ROOT;
/* search tree for object (with OBJECT_PERCPU flag) boundaries */
static struct rb_root object_percpu_tree_root = RB_ROOT;
/* protecting the access to object_list, object_tree_root (or object_phys_tree_root) */
static DEFINE_RAW_SPINLOCK(kmemleak_lock);
@ -298,7 +300,7 @@ static void hex_dump_object(struct seq_file *seq,
const u8 *ptr = (const u8 *)object->pointer;
size_t len;
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
if (WARN_ON_ONCE(object->flags & (OBJECT_PHYS | OBJECT_PERCPU)))
return;
/* limit the number of lines to HEX_MAX_LINES */
@ -390,6 +392,15 @@ static void dump_object_info(struct kmemleak_object *object)
stack_depot_print(object->trace_handle);
}
static struct rb_root *object_tree(unsigned long objflags)
{
if (objflags & OBJECT_PHYS)
return &object_phys_tree_root;
if (objflags & OBJECT_PERCPU)
return &object_percpu_tree_root;
return &object_tree_root;
}
/*
* Look-up a memory block metadata (kmemleak_object) in the object search
* tree based on a pointer value. If alias is 0, only values pointing to the
@ -397,10 +408,9 @@ static void dump_object_info(struct kmemleak_object *object)
* when calling this function.
*/
static struct kmemleak_object *__lookup_object(unsigned long ptr, int alias,
bool is_phys)
unsigned int objflags)
{
struct rb_node *rb = is_phys ? object_phys_tree_root.rb_node :
object_tree_root.rb_node;
struct rb_node *rb = object_tree(objflags)->rb_node;
unsigned long untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
while (rb) {
@ -429,7 +439,7 @@ static struct kmemleak_object *__lookup_object(unsigned long ptr, int alias,
/* Look-up a kmemleak object which allocated with virtual address. */
static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
{
return __lookup_object(ptr, alias, false);
return __lookup_object(ptr, alias, 0);
}
/*
@ -542,14 +552,14 @@ static void put_object(struct kmemleak_object *object)
* Look up an object in the object search tree and increase its use_count.
*/
static struct kmemleak_object *__find_and_get_object(unsigned long ptr, int alias,
bool is_phys)
unsigned int objflags)
{
unsigned long flags;
struct kmemleak_object *object;
rcu_read_lock();
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __lookup_object(ptr, alias, is_phys);
object = __lookup_object(ptr, alias, objflags);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
/* check whether the object is still available */
@ -563,19 +573,16 @@ static struct kmemleak_object *__find_and_get_object(unsigned long ptr, int alia
/* Look up and get an object which allocated with virtual address. */
static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
{
return __find_and_get_object(ptr, alias, false);
return __find_and_get_object(ptr, alias, 0);
}
/*
* Remove an object from the object_tree_root (or object_phys_tree_root)
* and object_list. Must be called with the kmemleak_lock held _if_ kmemleak
* is still enabled.
* Remove an object from its object tree and object_list. Must be called with
* the kmemleak_lock held _if_ kmemleak is still enabled.
*/
static void __remove_object(struct kmemleak_object *object)
{
rb_erase(&object->rb_node, object->flags & OBJECT_PHYS ?
&object_phys_tree_root :
&object_tree_root);
rb_erase(&object->rb_node, object_tree(object->flags));
if (!(object->del_state & DELSTATE_NO_DELETE))
list_del_rcu(&object->object_list);
object->del_state |= DELSTATE_REMOVED;
@ -583,11 +590,11 @@ static void __remove_object(struct kmemleak_object *object)
static struct kmemleak_object *__find_and_remove_object(unsigned long ptr,
int alias,
bool is_phys)
unsigned int objflags)
{
struct kmemleak_object *object;
object = __lookup_object(ptr, alias, is_phys);
object = __lookup_object(ptr, alias, objflags);
if (object)
__remove_object(object);
@ -595,19 +602,18 @@ static struct kmemleak_object *__find_and_remove_object(unsigned long ptr,
}
/*
* Look up an object in the object search tree and remove it from both
* object_tree_root (or object_phys_tree_root) and object_list. The
* returned object's use_count should be at least 1, as initially set
* by create_object().
* Look up an object in the object search tree and remove it from both object
* tree root and object_list. The returned object's use_count should be at
* least 1, as initially set by create_object().
*/
static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias,
bool is_phys)
unsigned int objflags)
{
unsigned long flags;
struct kmemleak_object *object;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __find_and_remove_object(ptr, alias, is_phys);
object = __find_and_remove_object(ptr, alias, objflags);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
return object;
@ -678,7 +684,7 @@ static struct kmemleak_object *__alloc_object(gfp_t gfp)
}
static int __link_object(struct kmemleak_object *object, unsigned long ptr,
size_t size, int min_count, bool is_phys)
size_t size, int min_count, unsigned int objflags)
{
struct kmemleak_object *parent;
@ -686,7 +692,7 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
unsigned long untagged_ptr;
unsigned long untagged_objp;
object->flags = OBJECT_ALLOCATED | (is_phys ? OBJECT_PHYS : 0);
object->flags = OBJECT_ALLOCATED | objflags;
object->pointer = ptr;
object->size = kfence_ksize((void *)ptr) ?: size;
object->min_count = min_count;
@ -697,12 +703,11 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
* Only update min_addr and max_addr with object
* storing virtual address.
*/
if (!is_phys) {
if (!(objflags & (OBJECT_PHYS | OBJECT_PERCPU))) {
min_addr = min(min_addr, untagged_ptr);
max_addr = max(max_addr, untagged_ptr + size);
}
link = is_phys ? &object_phys_tree_root.rb_node :
&object_tree_root.rb_node;
link = &object_tree(objflags)->rb_node;
rb_parent = NULL;
while (*link) {
rb_parent = *link;
@ -724,8 +729,7 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
}
}
rb_link_node(&object->rb_node, rb_parent, link);
rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
&object_tree_root);
rb_insert_color(&object->rb_node, object_tree(objflags));
list_add_tail_rcu(&object->object_list, &object_list);
return 0;
@ -733,11 +737,10 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
/*
* Create the metadata (struct kmemleak_object) corresponding to an allocated
* memory block and add it to the object_list and object_tree_root (or
* object_phys_tree_root).
* memory block and add it to the object_list and object tree.
*/
static void __create_object(unsigned long ptr, size_t size,
int min_count, gfp_t gfp, bool is_phys)
int min_count, gfp_t gfp, unsigned int objflags)
{
struct kmemleak_object *object;
unsigned long flags;
@ -748,7 +751,7 @@ static void __create_object(unsigned long ptr, size_t size,
return;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
ret = __link_object(object, ptr, size, min_count, is_phys);
ret = __link_object(object, ptr, size, min_count, objflags);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
if (ret)
mem_pool_free(object);
@ -758,14 +761,21 @@ static void __create_object(unsigned long ptr, size_t size,
static void create_object(unsigned long ptr, size_t size,
int min_count, gfp_t gfp)
{
__create_object(ptr, size, min_count, gfp, false);
__create_object(ptr, size, min_count, gfp, 0);
}
/* Create kmemleak object which allocated with physical address. */
static void create_object_phys(unsigned long ptr, size_t size,
int min_count, gfp_t gfp)
{
__create_object(ptr, size, min_count, gfp, true);
__create_object(ptr, size, min_count, gfp, OBJECT_PHYS);
}
/* Create kmemleak object corresponding to a per-CPU allocation. */
static void create_object_percpu(unsigned long ptr, size_t size,
int min_count, gfp_t gfp)
{
__create_object(ptr, size, min_count, gfp, OBJECT_PERCPU);
}
/*
@ -792,11 +802,11 @@ static void __delete_object(struct kmemleak_object *object)
* Look up the metadata (struct kmemleak_object) corresponding to ptr and
* delete it.
*/
static void delete_object_full(unsigned long ptr)
static void delete_object_full(unsigned long ptr, unsigned int objflags)
{
struct kmemleak_object *object;
object = find_and_remove_object(ptr, 0, false);
object = find_and_remove_object(ptr, 0, objflags);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Freeing unknown object at 0x%08lx\n",
@ -812,7 +822,8 @@ static void delete_object_full(unsigned long ptr)
* delete it. If the memory block is partially freed, the function may create
* additional metadata for the remaining parts of the block.
*/
static void delete_object_part(unsigned long ptr, size_t size, bool is_phys)
static void delete_object_part(unsigned long ptr, size_t size,
unsigned int objflags)
{
struct kmemleak_object *object, *object_l, *object_r;
unsigned long start, end, flags;
@ -826,7 +837,7 @@ static void delete_object_part(unsigned long ptr, size_t size, bool is_phys)
goto out;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __find_and_remove_object(ptr, 1, is_phys);
object = __find_and_remove_object(ptr, 1, objflags);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
@ -844,11 +855,11 @@ static void delete_object_part(unsigned long ptr, size_t size, bool is_phys)
end = object->pointer + object->size;
if ((ptr > start) &&
!__link_object(object_l, start, ptr - start,
object->min_count, is_phys))
object->min_count, objflags))
object_l = NULL;
if ((ptr + size < end) &&
!__link_object(object_r, ptr + size, end - ptr - size,
object->min_count, is_phys))
object->min_count, objflags))
object_r = NULL;
unlock:
@ -879,11 +890,11 @@ static void paint_it(struct kmemleak_object *object, int color)
raw_spin_unlock_irqrestore(&object->lock, flags);
}
static void paint_ptr(unsigned long ptr, int color, bool is_phys)
static void paint_ptr(unsigned long ptr, int color, unsigned int objflags)
{
struct kmemleak_object *object;
object = __find_and_get_object(ptr, 0, is_phys);
object = __find_and_get_object(ptr, 0, objflags);
if (!object) {
kmemleak_warn("Trying to color unknown object at 0x%08lx as %s\n",
ptr,
@ -901,16 +912,16 @@ static void paint_ptr(unsigned long ptr, int color, bool is_phys)
*/
static void make_gray_object(unsigned long ptr)
{
paint_ptr(ptr, KMEMLEAK_GREY, false);
paint_ptr(ptr, KMEMLEAK_GREY, 0);
}
/*
* Mark the object as black-colored so that it is ignored from scans and
* reporting.
*/
static void make_black_object(unsigned long ptr, bool is_phys)
static void make_black_object(unsigned long ptr, unsigned int objflags)
{
paint_ptr(ptr, KMEMLEAK_BLACK, is_phys);
paint_ptr(ptr, KMEMLEAK_BLACK, objflags);
}
/*
@ -1046,8 +1057,6 @@ EXPORT_SYMBOL_GPL(kmemleak_alloc);
void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
gfp_t gfp)
{
unsigned int cpu;
pr_debug("%s(0x%px, %zu)\n", __func__, ptr, size);
/*
@ -1055,9 +1064,7 @@ void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
* (min_count is set to 0).
*/
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
create_object((unsigned long)per_cpu_ptr(ptr, cpu),
size, 0, gfp);
create_object_percpu((unsigned long)ptr, size, 0, gfp);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
@ -1098,7 +1105,7 @@ void __ref kmemleak_free(const void *ptr)
pr_debug("%s(0x%px)\n", __func__, ptr);
if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
delete_object_full((unsigned long)ptr);
delete_object_full((unsigned long)ptr, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free);
@ -1116,7 +1123,7 @@ void __ref kmemleak_free_part(const void *ptr, size_t size)
pr_debug("%s(0x%px)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
delete_object_part((unsigned long)ptr, size, false);
delete_object_part((unsigned long)ptr, size, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free_part);
@ -1129,14 +1136,10 @@ EXPORT_SYMBOL_GPL(kmemleak_free_part);
*/
void __ref kmemleak_free_percpu(const void __percpu *ptr)
{
unsigned int cpu;
pr_debug("%s(0x%px)\n", __func__, ptr);
if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
delete_object_full((unsigned long)per_cpu_ptr(ptr,
cpu));
delete_object_full((unsigned long)ptr, OBJECT_PERCPU);
}
EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
@ -1206,7 +1209,7 @@ void __ref kmemleak_ignore(const void *ptr)
pr_debug("%s(0x%px)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
make_black_object((unsigned long)ptr, false);
make_black_object((unsigned long)ptr, 0);
}
EXPORT_SYMBOL(kmemleak_ignore);
@ -1280,7 +1283,7 @@ void __ref kmemleak_free_part_phys(phys_addr_t phys, size_t size)
pr_debug("%s(0x%px)\n", __func__, &phys);
if (kmemleak_enabled)
delete_object_part((unsigned long)phys, size, true);
delete_object_part((unsigned long)phys, size, OBJECT_PHYS);
}
EXPORT_SYMBOL(kmemleak_free_part_phys);
@ -1294,7 +1297,7 @@ void __ref kmemleak_ignore_phys(phys_addr_t phys)
pr_debug("%s(0x%px)\n", __func__, &phys);
if (kmemleak_enabled)
make_black_object((unsigned long)phys, true);
make_black_object((unsigned long)phys, OBJECT_PHYS);
}
EXPORT_SYMBOL(kmemleak_ignore_phys);
@ -1305,7 +1308,7 @@ static bool update_checksum(struct kmemleak_object *object)
{
u32 old_csum = object->checksum;
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
if (WARN_ON_ONCE(object->flags & (OBJECT_PHYS | OBJECT_PERCPU)))
return false;
kasan_disable_current();
@ -1461,7 +1464,6 @@ static void scan_object(struct kmemleak_object *object)
{
struct kmemleak_scan_area *area;
unsigned long flags;
void *obj_ptr;
/*
* Once the object->lock is acquired, the corresponding memory block
@ -1474,14 +1476,27 @@ static void scan_object(struct kmemleak_object *object)
/* already freed object */
goto out;
obj_ptr = object->flags & OBJECT_PHYS ?
__va((phys_addr_t)object->pointer) :
(void *)object->pointer;
if (object->flags & OBJECT_PERCPU) {
unsigned int cpu;
if (hlist_empty(&object->area_list) ||
for_each_possible_cpu(cpu) {
void *start = per_cpu_ptr((void __percpu *)object->pointer, cpu);
void *end = start + object->size;
scan_block(start, end, object);
raw_spin_unlock_irqrestore(&object->lock, flags);
cond_resched();
raw_spin_lock_irqsave(&object->lock, flags);
if (!(object->flags & OBJECT_ALLOCATED))
break;
}
} else if (hlist_empty(&object->area_list) ||
object->flags & OBJECT_FULL_SCAN) {
void *start = obj_ptr;
void *end = obj_ptr + object->size;
void *start = object->flags & OBJECT_PHYS ?
__va((phys_addr_t)object->pointer) :
(void *)object->pointer;
void *end = start + object->size;
void *next;
do {
@ -1496,11 +1511,12 @@ static void scan_object(struct kmemleak_object *object)
cond_resched();
raw_spin_lock_irqsave(&object->lock, flags);
} while (object->flags & OBJECT_ALLOCATED);
} else
} else {
hlist_for_each_entry(area, &object->area_list, node)
scan_block((void *)area->start,
(void *)(area->start + area->size),
object);
}
out:
raw_spin_unlock_irqrestore(&object->lock, flags);
}