mm/kmemleak.c: Use list_for_each_entry_safe to reconstruct function scan_gray_list
Subsystems (2)
PATCH 2/3 mm/kmemleak.c: Use list_for_each_entry_safe to reconstruct function scan_gray_list
--- mm/kmemleak.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
mm/kmemleak.c +1 -7
@@ -1225,22 +1225,16 @@ static void scan_gray_list(void)* from inside the loop. The kmemleak objects cannot be freed from * outside the loop because their use_count was incremented. */ - object =list_entry (gray_list.next,typeof (*object), gray_list); -while (&object->gray_list != &gray_list) { +list_for_each_entry_safe (object, tmp, &gray_list, gray_list) {cond_resched ();/* may add new objects to the list */ if (!scan_should_stop ())scan_object (object); - tmp =list_entry (object->gray_list.next,typeof (*object), - gray_list); -/* remove the object from the list and release it */ list_del (&object->gray_list);put_object (object); - - object = tmp; }WARN_ON (!list_empty (&gray_list)); }
Signature · 1 line
1.8.3.rc1.44.gb387c77
Catalin Marinas
maintainerQuoted 22 lines · majianpeng
Signed-off-by Jianpeng Ma <[email protected]>--- mm/kmemleak.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)mm/kmemleak.c +1
-2@@ -1225,22 +1225,16 @@ static void scan_gray_list(void)* from inside the loop. The kmemleak objects cannot be freed from * outside the loop because their use_count was incremented. */ - object =list_entry (gray_list.next,typeof (*object), gray_list); -while (&object->gray_list != &gray_list) { +list_for_each_entry_safe (object, tmp, &gray_list, gray_list) {cond_resched ();/* may add new objects to the list */ if (!scan_should_stop ())scan_object (object);
mm/kmemleak.c static void scan_gray_list(void) · line 1239
Quoted 10 lines
mm/kmemleak.c +0
-5- tmp =list_entry (object->gray_list.next,typeof (*object), - gray_list); -/* remove the object from the list and release it */ list_del (&object->gray_list);put_object (object); - - object = tmp; }WARN_ON (!list_empty (&gray_list));
I tried this patch for a few days and I hit the WARN_ON after the loop. During scanning, new entries may be added at the end of the loop but we need to loop until all the entries have been removed. I probably had a reason why I had the 'while' loop.
The key difference is that list_for_each_entry_safe() gets the next entry (n or tmp above) before scan_object() and it may hit the end of the list. However, scan_object() may do a list_add_tail(&gray_list) hence we need to get the next entry after this function.
Basically list_for_each_entry_safe() is not safe with tail additions. I'll revert this patch (hasn't reached mainline anyway).
Thanks.
Signature · 7 lines
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