On 11/15/19 4:35 PM, Muni Sekhar wrote:
[ Please keep me in CC as I'm not subscribed to the list] Hi All, My kernel is built with the following options: $ cat /boot/config-5.0.1 | grep NO_HZ CONFIG_NO_HZ_COMMON=y CONFIG_NO_HZ_IDLE=y # CONFIG_NO_HZ_FULL is not set CONFIG_NO_HZ=y CONFIG_RCU_FAST_NO_HZ=y I booted with watchdog enabled(nmi_watchdog=1) as given below: BOOT_IMAGE=/boot/vmlinuz-5.0.1 root=UUID=f65454ae-3f1d-4b9e-b4be-74a29becbe1e ro debug ignore_loglevel console=ttyUSB0,115200 console=tty0 console=tty1 console=ttyS2,115200 memmap=1M!1023M nmi_watchdog=1 crashkernel=384M-:128M When the system is frozen or the kernel is locked up(I noticed that in this state kernel is not responding for ALT-SysRq-<command key>) but watchdog is not triggered. So I want to understand how to enable the watchdog timer and how to verify the basic watchdog functionality behavior? > Any pointers on this will be greatly appreciated.
Sorry, I do not have an answer. Please note that you are talking about the NMI watchdog, which is completely unrelated to hardware watchdogs and not handled by the watchdog subsystem. I would suggest to send your question to the Linux kernel mailing list and clearly state that you are talking about the NMI watchdog. Please note that, for the NMI watchdog to do anything, you must have CONFIG_HARDLOCKUP_DETECTOR enabled in your kernel configuration. I don't know what if anything the configuration options you listed above have to do with the NMI watchdog. Another possibility, of course, might be to enable a hardware watchdog in your system (assuming it supports one). I personally would not trust the NMI watchdog because to detect a system hang, after all, there are situations where even NMIs no longer work. Guenter
