Although /dev/watchdog is available in usermode, but nothing should stop you to write to it from a kernel thread.
Rajat On Wed, Dec 4, 2013 at 5:50 PM, Peter Teoh <[email protected]> wrote: > > > > On Thu, Dec 5, 2013 at 9:06 AM, Vipul Jain <[email protected]> wrote: > >> >> >> >> On Wed, Dec 4, 2013 at 4:57 PM, <[email protected]> wrote: >> >>> 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. >>> >>> Hi Valdis, >> >> I see what you are saying but what if the user process that's feeding the >> dog gets hung and rest of the system is fine then it will bring the whole >> system down won't it? I basically want to avoid this? >> >> > Normally the process that feed the dog, is a simple process that JUST > periodically set the watchdog device descriptor. Yes, one main() with a > while loop just periodically resetting the descriptor. > > And so it is is not able to respond in time, by inference, OTHER PROCESS > must have hung. In other system i saw there is a mother process that > monitor a few (not all) of its key child process .... so perhaps one child > will have one variable to signal to the mother that it is running. If not > responding in time, the mother will clean up everything and then purposely > not setting the watchdog, resulting in reboot. > > >> Regards, >> Vipul. >> >> > > > -- > Regards, > Peter Teoh > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >
_______________________________________________ Kernelnewbies mailing list [email protected] http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
