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    SubjectRe: Kernel crash after using new Intel NIC (igb)
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    Le mardi 24 mai 2011 à 23:06 -0700, Arun Sharma a écrit :
    > On Wed, May 25, 2011 at 04:44:29AM +0200, Eric Dumazet wrote:
    > >
    > > Hmm, thanks for the report. Are you running x86 or another arch ?
    > >
    >
    > This was on x86.
    >
    > > We probably need some sort of memory barrier.
    > >
    > > However, locking this central lock makes the thing too slow, I'll try to
    > > use an atomic_inc_return on p->refcnt instead. (and then lock
    > > unused_peers.lock if we got a 0->1 transition)
    >
    > Another possibility is to do the list_empty() check twice. Once without
    > taking the lock and again with the spinlock held.
    >

    Why ?

    list_del_init(&p->unused); (done under lock of course) is safe, you can
    call it twice, no problem.

    No, the real problem is the (!list_empty(&p->unused) test : It seems to
    not always tell the truth if not done under lock.



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