Re: [PATCH] ext4: avoid huge mmp update interval value

[Theodore Ts'o]

On Thu, Aug 05, 2021 at 06:14:18PM +0300, Pavel Skripkin wrote:
> Syzbot reported task hung bug in ext4_fill_super(). The problem was in
> too huge mmp update interval.
> 
> Syzkaller reproducer setted s_mmp_update_interval to 39785 seconds. This
> update interaval is unreasonable huge and it can cause tasks to hung on
> kthread_stop() call, since it will wait until timeout timer expires.

I must be missing something.  kthread_stop() should wake up the
kmmpd() thread, which should see kthread_should_stop(), and then it
should exit.  What is causing it to wait until the timeout timer
expires?

					- Ted