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Date:   Mon, 18 Nov 2019 08:38:38 -0600
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Muni Sekhar <munisekharrms@gmail.com>
Cc:     linux-watchdog@vger.kernel.org, wim@linux-watchdog.org,
        linux@roeck-us.net
Subject: Re: watchdog: how to enable?
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[-cc linux-pci (nothing here is PCI-specific)]

On Sat, Nov 16, 2019 at 06:05:05AM +0530, Muni Sekhar wrote:
> 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?

I don't know much about the watchdog, but I assume you've found these
already?

  Documentation/admin-guide/lockup-watchdogs.rst
  Documentation/admin-guide/sysctl/kernel.rst

Do you have CONFIG_HAVE_NMI_WATCHDOG=y?  (See arch/Kconfig)