On Tue, 2018-12-11 at 18:03 -0500, Dennis Zhou wrote: +AD4 diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c +AD4 index 6bd0619a7d6e..c30661ddc873 100644 +AD4 --- a/block/blk-cgroup.c +AD4 +-+-+- b/block/blk-cgroup.c +AD4 +AEAAQA -202,6 +-202,12 +AEAAQA static struct blkcg+AF8-gq +ACo-blkg+AF8-create(struct blkcg +ACo-blkcg, +AD4 WARN+AF8-ON+AF8-ONCE(+ACE-rcu+AF8-read+AF8-lock+AF8-held())+ADs +AD4 lockdep+AF8-assert+AF8-held(+ACY-q-+AD4-queue+AF8-lock)+ADs +AD4 +AD4 +- /+ACo request+AF8-queue is dying, do not create/recreate a blkg +ACo-/ +AD4 +- if (blk+AF8-queue+AF8-dying(q)) +AHs +AD4 +- ret +AD0 -ENODEV+ADs +AD4 +- goto err+AF8-free+AF8-blkg+ADs +AD4 +- +AH0 +AD4 +- +AD4 /+ACo blkg holds a reference to blkcg +ACo-/ +AD4 if (+ACE-css+AF8-tryget+AF8-online(+ACY-blkcg-+AD4-css)) +AHs +AD4 ret +AD0 -ENODEV+ADs What prevents that the queue state changes after blk+AF8-queue+AF8-dying() has returned and before blkg+AF8-create() returns? Are you sure you don't need to protect this code with a blk+AF8-queue+AF8-enter() / blk+AF8-queue+AF8-exit() pair? Bart.
