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-rw-r--r--kernel/exit.c16
1 files changed, 6 insertions, 10 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index c9e5a1c14e08..f923724ab3c9 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -642,35 +642,31 @@ retry:
642 /* 642 /*
643 * We found no owner yet mm_users > 1: this implies that we are 643 * We found no owner yet mm_users > 1: this implies that we are
644 * most likely racing with swapoff (try_to_unuse()) or /proc or 644 * most likely racing with swapoff (try_to_unuse()) or /proc or
645 * ptrace or page migration (get_task_mm()). Mark owner as NULL, 645 * ptrace or page migration (get_task_mm()). Mark owner as NULL.
646 * so that subsystems can understand the callback and take action.
647 */ 646 */
648 down_write(&mm->mmap_sem);
649 cgroup_mm_owner_callbacks(mm->owner, NULL);
650 mm->owner = NULL; 647 mm->owner = NULL;
651 up_write(&mm->mmap_sem);
652 return; 648 return;
653 649
654assign_new_owner: 650assign_new_owner:
655 BUG_ON(c == p); 651 BUG_ON(c == p);
656 get_task_struct(c); 652 get_task_struct(c);
657 read_unlock(&tasklist_lock);
658 down_write(&mm->mmap_sem);
659 /* 653 /*
660 * The task_lock protects c->mm from changing. 654 * The task_lock protects c->mm from changing.
661 * We always want mm->owner->mm == mm 655 * We always want mm->owner->mm == mm
662 */ 656 */
663 task_lock(c); 657 task_lock(c);
658 /*
659 * Delay read_unlock() till we have the task_lock()
660 * to ensure that c does not slip away underneath us
661 */
662 read_unlock(&tasklist_lock);
664 if (c->mm != mm) { 663 if (c->mm != mm) {
665 task_unlock(c); 664 task_unlock(c);
666 up_write(&mm->mmap_sem);
667 put_task_struct(c); 665 put_task_struct(c);
668 goto retry; 666 goto retry;
669 } 667 }
670 cgroup_mm_owner_callbacks(mm->owner, c);
671 mm->owner = c; 668 mm->owner = c;
672 task_unlock(c); 669 task_unlock(c);
673 up_write(&mm->mmap_sem);
674 put_task_struct(c); 670 put_task_struct(c);
675} 671}
676#endif /* CONFIG_MM_OWNER */ 672#endif /* CONFIG_MM_OWNER */