watchdog pet in kernel module

[Valdis.Kletnieks at vt.edu]

On Wed, 04 Dec 2013 16:45:44 -0800, Vipul Jain said:

> If you don't mind can you please provide me more insight as what can be
> false alarm I can encounter to move pet inside kernel module?

The issue isn't false alarms - it's failure to alarm when it should.

The problem is that it's possible for a kernel to get wedged in such a way that
a kernel thread is still able to feed the watchdog timer on a regular basis,
but userspace is effectively hung and unable to proceed.  For example, if an
OOPS happens while a filesystem lock is held, all future userspace references
to that filesystem (and possibly all filesystems of the same type) will hang,
eventually strangling the box while the kernel is still perfectly able to keep
the watchdog working.

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