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    SubjectRe: Unable to kill processes in D-state
    On Sat, Oct 05, 2002 at 02:11:02PM -0400, Robert Love wrote:
    > On Sat, 2002-10-05 at 05:07, Thomas Lang?s wrote:
    >
    > > We have a fairly large installation on-campus, and we have some problems
    > > with the current linux-kernel (and older ones) - namely that processes
    > > entering D-state will stay there forever (given that the right event got
    > > them there in the first place). This right event is killing the
    > > autofs-daemon. Doing this will result in heavy load because of lots
    > > of D-state processes, and you can't kill any of the D-state processes.
    > > Why shouldn't one be able to kill processes that has entered D-state?
    > > We have to reboot our servers to get rid of this problem, and it's
    > > rather annoying.
    >
    > Because they are in uninterruptible sleep. They are doing something
    > important, presumably in a critical section, and have no wake-up path
    > for signals or errors.
    >
    > Finally, they probably hold a semaphore. In short, you cannot kill
    > them, nor would you want to.
    >
    > I would simplify the question and ask why are you killing the autofs
    > daemon? Clearly this is a recipe for disaster.

    On the other hand it's a bug if a process stays in D-state for time of
    order of seconds or more. Unfortunately it's impossible to avoid this
    in networking filesystems with current state of VFS (in 2.4). Even there
    though, it's a bug if it's indefinite.

    These problems were already discussed on LKML, you might want to search
    the archive. IIRC this is a known problem of OpenAFS (not in standart
    kernel). It was reported with various drivers for some 2.4.x kernels
    too.

    -------------------------------------------------------------------------------
    Jan 'Bulb' Hudec <bulb@ucw.cz>
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