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    SubjectRe: [PATCH] llist: Fix missing lockless_dereference()
    On Sun, Feb 08, 2015 at 02:12:04PM +1300, Michael Cree wrote:
    > On Sun, Feb 08, 2015 at 08:59:41AM +0800, Greg KH wrote:
    > > On Sun, Feb 08, 2015 at 01:47:29PM +1300, Michael Cree wrote:
    > > > On Sat, Feb 07, 2015 at 10:30:44PM +0000, Mathieu Desnoyers wrote:
    > > > > > On Fri, Feb 06, 2015 at 09:08:21PM -0500, Mathieu Desnoyers wrote:
    > > > > > > A lockless_dereference() appears to be missing in llist_del_first().
    > > > > > > It should only matter for Alpha in practice.
    > > >
    > > > What could one anticipate to be the symptoms of such a missing
    > > > lockless_dereference()?
    > > >
    > > > The Alpha kernel is behaving pretty well provided one builds a machine
    > > > specific kernel and UP. When running an SMP kernel some packages
    > > > (most notably the java runtime, but there are a few others) occasionally
    > > > lock up in a pthread call --- could be a problem in libc rather then the
    > > > kernel.
    > >
    > > Hm, if only UP alpha needs to be supported, odds are we could rip a lot
    > > of odd stuff out of the kernel that deals with memory barriers and other
    > > nasty locking things that the Alpha requires.
    > >
    > > Would that be ok? Or is someone somewhere going to want to be running a
    > > SMP kernel on Alpha in the future?
    >
    > I am running an SMP kernel on a 3-cpu Alpha system; it mostly works
    > just fine.
    >
    > I was just noting that there is something up with java---it locks up
    > occassionally in a pthread call, and there are a few other packages
    > that occasionally fail in test suites when being built under an SMP
    > kernel but always pass when built under an UP kernel which suggests
    > there is a little buglet somewhere in the SMP code, either in the
    > kernel or in libc.
    >
    > Running an SMP system for the Debian Alpha build daemon at debian-ports
    > is really useful for keeping up with the other architectures.

    Ok, sorry, I got the impression that you weren't running a SMP kernel,
    nevermind then, we'll go back to keeping this ancient beast alive :)

    greg k-h


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