On Tue, Jan 28, 2020 at 12:11 AM Georgi Nikolov <gnikolov@xxxxxxxxxxx> wrote: > > Yes the kernel is 4.19.67-2+deb10u2. I have tried with 5.4.8-1~bpo10+1 > and same thing happened. > Before this i have used same thing for a long time with kernel 4.9.189-3. > It happens most often when there is some heavy IO. Thanks for the information. I suspect the hang is waiting for md_lock(). Could you please dump the mdX_raid6 stack when the hang happens? You can do it by: cat /proc/$(pidof mdX_raid6)/stack Thanks, Song