Killing processes from DDB

Matt Burke mattblists at
Thu Aug 30 10:12:50 UTC 2012

On 08/30/12 09:12, Konstantin Belousov wrote:
> Stop state indicates that the process is stopped or being stopped. The later
> is your case. The process has one thread executing exit1() kernel function,
> which terminates the process. In the course of work, the function notifies
> all other threads of the exiting process that they shall terminate ASAP at
> the next safe point.

Thanks for the explanation - I thought stop state was just a mechanism for
processes to pause (as in ^Z from the shell) by being skipped by the
scheduler or something... Looking in /sys/kern I think I need to do a lot
of reading to correct what appear to be some bad assumptions I've picked up
over the years.

> The way to debug the issue is to break into ddb on console and get
> a backtrace for the spinning thread, then continue, then break again
> and get another backtrace. Do it several times, to see where the code
> spins.


> It is impossible to even start guessing what is wrong, without seeing
> the backtrace.
> Still, recompiling VB could be good idea, since VB kernel module uses
> non-stable KPI and KBI, thus what you see might be just build issue.

Indeed, however I find Bad Things happening are a great excuse to learn
more about the system's innards ;)


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