echo c > /proc/sysrq-trigger doesn't reboot the system

I am trying to collect a core dump in result of kernel panic. Installed and configured kdump, but when executing echo c > /proc/sysrq-trigger, everything just hangs and the reboot doesn't happen. I don't even get any output in the result of running the command. RAM size is 4GB. The following is the output of `kdump-config show' DUMP_MODE: kdump USE_KDUMP: 1 KDUMP_SYSCTL: kernel.panic_on_oops=1 KDUMP_COREDIR: /var/crash crashkernel addr: 0x /var/lib/kdump/vmlinuz: symbolic link to /boot/vmlinuz-4.9.0-dev kdump initrd: /var/lib/kdump/initrd.img: symbolic link to /var/lib/kdump/initrd.img-4.9.0-dev current state: ready to kdump kexec command: /sbin/kexec -p --command-line="BOOT_IMAGE=/boot/vmlinuz-4.9.0-dev root=UUID=b395d695-7bb2-408b-a61b-b5188fc5b900 ro resume=UUID=19e8dc56-ff6d-40de-84ec-b9abd7399591 debug net.ifnames=0 biosdevname=0 ignore_loglevel intel_iommu=on,igfx_off intremap=no_x2apic_optout irqpoll noirqdistrib nr_cpus=1 nousb systemd.unit=kdump-tools.service" --initrd=/var/lib/kdump/initrd.img /var/lib/kdump/vmlinuz Ubuntu 16.04. Kernel 4.9.0