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    SubjectRe: is killing zombies possible w/o a reboot?
    On Thu, Nov 04, 2004 at 08:39:34AM +0200, Denis Vlasenko wrote:
    > On Thursday 04 November 2004 01:33, Russell Miller wrote:
    > > On Wednesday 03 November 2004 17:03, Doug McNaught wrote:
    > >
    > > > It was already mentioned in this thread that the bookkeeping required
    > > > to clean up properly from such an abort would add a lot of overhead
    > > > and slow down the normal, non-buggy case.
    > > >
    > > I am going to continue pursuing this at the risk of making a bigger fool of
    > > myself than I already am, but I want to make sure that I understand the
    > > issues - and I did read the message you are referring to.
    > >
    > > I think what you are saying is that there is kind of a race condition here.
    > > When something is on the wait queue, it has to be followed through to
    > > completion. An interrupt could be received at any time, and if it's taken
    > > off of the wait queue prematurely, it'll crash the kernel, because the
    > > interrupt has no way of telling that.
    > The problem is in locking. You must not kill process while it is
    > in uninterruptible state because it is uninterruptible
    > for a reason - has taken semaphore, or get_cpu(), etc.
    > You do want it to do put_cpu(), right?
    > Processes must never get stuck in D, it's a kernel bug.
    > Find out how did process ended up in D state forever,
    > and fix it - that's what I'm trying to do
    > in these cases.

    Perhaps it would be useful to add some debugging to the kernel for these
    cases, somewhat akin to Ingo's preempt trace stuff?

    If a process is in D state and receives a SIGKILL, assume it must exit
    within a few seconds or it's a bug, and dump as much information about
    it as is practical...?


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