kmemleak: Allow rescheduling during an object scanning

If the object size is bigger than a predefined value (4K in this case),
release the object lock during scanning and call cond_resched().
Re-acquire the lock after rescheduling and test whether the object is
still valid.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 17 insertions, 4 deletions

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 487267310a84..6debe0d80e64 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -107,6 +107,7 @@
 #define SECS_FIRST_SCAN         60      /* delay before the first scan */
 #define SECS_SCAN_WAIT          600     /* subsequent auto scanning delay */
 #define GRAY_LIST_PASSES        25      /* maximum number of gray list scans */
+#define MAX_SCAN_SIZE           4096    /* maximum size of a scanned block */
 
 #define BYTES_PER_POINTER       sizeof(void *)
 
@@ -642,6 +643,7 @@ static void make_black_object(unsigned long ptr)
 
         spin_lock_irqsave(&object->lock, flags);
         object->min_count = -1;
+        object->flags |= OBJECT_NO_SCAN;
         spin_unlock_irqrestore(&object->lock, flags);
         put_object(object);
 }
@@ -949,10 +951,21 @@ static void scan_object(struct kmemleak_object *object)
         if (!(object->flags & OBJECT_ALLOCATED))
                 /* already freed object */
                 goto out;
-        if (hlist_empty(&object->area_list))
-                scan_block((void *)object->pointer,
-                           (void *)(object->pointer + object->size), object, 0);
-        else
+        if (hlist_empty(&object->area_list)) {
+                void *start = (void *)object->pointer;
+                void *end = (void *)(object->pointer + object->size);
+
+                while (start < end && (object->flags & OBJECT_ALLOCATED) &&
+                       !(object->flags & OBJECT_NO_SCAN)) {
+                        scan_block(start, min(start + MAX_SCAN_SIZE, end),
+                                   object, 0);
+                        start += MAX_SCAN_SIZE;
+
+                        spin_unlock_irqrestore(&object->lock, flags);
+                        cond_resched();
+                        spin_lock_irqsave(&object->lock, flags);
+                }
+        } else
                 hlist_for_each_entry(area, elem, &object->area_list, node)
                         scan_block((void *)(object->pointer + area->offset),
                                    (void *)(object->pointer + area->offset