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,
Kuai
