On Wed, Apr 26, 2023 at 09:13:08AM +0800, Yu Kuai wrote: > Hi, > > 在 2023/04/25 19:09, Yu Kuai 写道: > > Hi, > > > > 在 2023/04/25 17:41, Tao Su 写道: > > > On Tue, Apr 25, 2023 at 04:09:34PM +0800, Yu Kuai wrote: > > > > Hi, > > > > > > > > 在 2023/04/25 15:59, Tao Su 写道: > > > > > Kernel hang when poweroff or reboot, due to infinite restart > > > > > in function > > > > > blkg_destroy_all. It will goto restart label when a batch of blkgs are > > > > > destroyed, but not remove blkg node in blkg_list. So the blkg_list is > > > > > same in every 'restart' and result in kernel hang. > > > > > > > > > > By adding list_del to remove blkg node after destroying, can solve this > > > > > kernel hang issue and satisfy the previous will to 'restart'. > > > > > > > > > > Reported-by: Xiangfei Ma <xiangfeix.ma@xxxxxxxxx> > > > > > Tested-by: Xiangfei Ma <xiangfeix.ma@xxxxxxxxx> > > > > > Tested-by: Farrah Chen <farrah.chen@xxxxxxxxx> > > > > > Signed-off-by: Tao Su <tao1.su@xxxxxxxxxxxxxxx> > > > > > --- > > > > > block/blk-cgroup.c | 1 + > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > > > > > index bd50b55bdb61..960eb538a704 100644 > > > > > --- a/block/blk-cgroup.c > > > > > +++ b/block/blk-cgroup.c > > > > > @@ -530,6 +530,7 @@ static void blkg_destroy_all(struct gendisk *disk) > > > > > spin_lock(&blkcg->lock); > > > > > blkg_destroy(blkg); > > > > > + list_del(&blkg->q_node); > > > > > > > > blkg should stay on the queue list until blkg_free_workfn(), otherwise > > > > parent blkg can be freed before child, which will cause some known > > > > issue. > > > > > > Yes, directly removing blkg node is not appropriate, which I noticed some > > > comments in blkg_destroy(), thanks for pointing out this issue. > > > > > > > > > > > I think this hung happens when total blkg is greater than > > > > BLKG_DESTROY_BATCH_SIZE, right? > > > > > > Yes, you are right. > > > > > > > > > > > Can you try if following patch fix your problem? > > > > > > This patch can also fix my problem, and indeed is a more secure way. > > > > Thanks for the test, for a better solution, I think 'blkcg_mutex' can > > be used to protect 'blkg->q_node' list instead of 'queue_lock', so that > > the 'restart' can be removed because softlockup can be avoided. > > > > I looked into this, and I found that this is not a easy thing to do. > > Anyway, feel free to submit a new patch based on my orignial suggestion. Thanks for your contribution and careful review, I will submit the new patch if no other comments. Thanks, Tao > > Thanks, > Kuai >
