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>

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 487267310a8447a175ede900f69c35ca55d63dba..6debe0d80e641bfe31e6c32243a154f920c55280 100644 (file)
--- 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