kmemleak: Add more cond_resched() calls in the scanning thread

Following recent fix to no longer reschedule in the scan_block()
function, the system may become unresponsive with !PREEMPT. This patch
re-adds the cond_resched() call to scan_block() but conditioned by the
allow_resched parameter.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 8 deletions

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 60065531f60c..93f14818e901 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -807,7 +807,7 @@ static int scan_should_stop(void)
  * found to the gray list.
  */
 static void scan_block(void *_start, void *_end,
-                       struct kmemleak_object *scanned)
+                       struct kmemleak_object *scanned, int allow_resched)
 {
         unsigned long *ptr;
         unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
@@ -818,6 +818,8 @@ static void scan_block(void *_start, void *_end,
                 unsigned long pointer = *ptr;
                 struct kmemleak_object *object;
 
+                if (allow_resched)
+                        cond_resched();
                 if (scan_should_stop())
                         break;
 
@@ -881,12 +883,12 @@ static void scan_object(struct kmemleak_object *object)
                 goto out;
         if (hlist_empty(&object->area_list))
                 scan_block((void *)object->pointer,
-                           (void *)(object->pointer + object->size), object);
+                           (void *)(object->pointer + object->size), object, 0);
         else
                 hlist_for_each_entry(area, elem, &object->area_list, node)
                         scan_block((void *)(object->pointer + area->offset),
                                    (void *)(object->pointer + area->offset
-                                            + area->length), object);
+                                            + area->length), object, 0);
 out:
         spin_unlock_irqrestore(&object->lock, flags);
 }
@@ -931,14 +933,14 @@ static void kmemleak_scan(void)
         rcu_read_unlock();
 
         /* data/bss scanning */
-        scan_block(_sdata, _edata, NULL);
-        scan_block(__bss_start, __bss_stop, NULL);
+        scan_block(_sdata, _edata, NULL, 1);
+        scan_block(__bss_start, __bss_stop, NULL, 1);
 
 #ifdef CONFIG_SMP
         /* per-cpu sections scanning */
         for_each_possible_cpu(i)
                 scan_block(__per_cpu_start + per_cpu_offset(i),
-                           __per_cpu_end + per_cpu_offset(i), NULL);
+                           __per_cpu_end + per_cpu_offset(i), NULL, 1);
 #endif
 
         /*
@@ -960,7 +962,7 @@ static void kmemleak_scan(void)
                         /* only scan if page is in use */
                         if (page_count(page) == 0)
                                 continue;
-                        scan_block(page, page + 1, NULL);
+                        scan_block(page, page + 1, NULL, 1);
                 }
         }
 
@@ -972,7 +974,8 @@ static void kmemleak_scan(void)
                 read_lock(&tasklist_lock);
                 for_each_process(task)
                         scan_block(task_stack_page(task),
-                                   task_stack_page(task) + THREAD_SIZE, NULL);
+                                   task_stack_page(task) + THREAD_SIZE,
+                                   NULL, 0);
                 read_unlock(&tasklist_lock);
         }