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    SubjectRe: [PATCH] random: Fix kernel panic due to system_wq use before init
    On 09/14/2016 05:06 PM, Linus Torvalds wrote:
    > On Wed, Sep 14, 2016 at 12:34 PM, Waiman Long<waiman.long@hpe.com> wrote:
    >> I can try, but the 16-socket system that I have at the moment takes a long
    >> time (more than an hour) for one shutdown-reboot cycle. It may not be really
    >> more interrupts in 4.8, it may be that the random driver just somehow run
    >> very slow on my test machine as it seems to have a major rewrite in the 4.8
    >> cycle.
    > Looking at the random driver updates since 4.7, the only thing I see
    > is that .crng_fast_load() for the chacha20 randomness. And that should
    > trigger only until it's been initialized, so the cost looks like it
    > should be limited.
    >
    > Is there some fundamental reason you think it's the random driver?
    > Other than the oops? Because I'd be more inclined to suspect just some
    > apic issue or something, where an actual interrupt line ends up
    > screaming or whatever. Is this UV? There's also the CPU hotplug state
    > machine changes etc.

    Yes, it is because of the oops that I suspect the random driver may be
    the cause.


    > But a few rounds of bisecting should hopefully cut down on the
    > suspects a lot. A *full* bisect might be 16-17 rounds, but if you can
    > do just four or five rounds of bisection, that should still cut it
    > down from 14k commits to "only" several hundred..
    >
    > Linus

    Yes, I will do a few rounds to see if we can isolate the problem. In the
    mean time, I will also reconfigure the system with less sockets to see
    if it is reproduced in a smaller configuration.

    Cheers,
    Longman

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