On 10/09/2024 20.30, Linus Torvalds wrote:

On Tue, 10 Sept 2024 at 10:53, Jesper Dangaard Brouer [off-list ref] wrote:

quoted

af2814149883e2c1851866ea2afcd8eadc040f79 is the first bad commit

Just for fun - can you test moving the queue freezing *inside* the
mutex, ie something like

   --- a/block/blk-sysfs.c
   +++ b/block/blk-sysfs.c
   @@ -670,11 +670,11 @@ queue_attr_store(struct kobject *kobj, struct
attribute *attr,
           if (!entry->store)
                   return -EIO;

   -       blk_mq_freeze_queue(q);
           mutex_lock(&q->sysfs_lock);
   +       blk_mq_freeze_queue(q);
           res = entry->store(disk, page, length);
   -       mutex_unlock(&q->sysfs_lock);
           blk_mq_unfreeze_queue(q);
   +       mutex_unlock(&q->sysfs_lock);
           return res;
    }

(Just do it by hand, my patch is whitespace-damaged on purpose -
untested and not well thought through).

Because I'm wondering whether maybe some IO is done under the
sysfs_lock, and then you might have a deadlock?

               Linus

Tested the patch (manually applied change) and it did NOT help.

More likely the patch/fix Jens pointed to is the culprit.

--Jesper