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    SubjectRe: [RFC][PATCHv6 00/12] printk: introduce printing kernel thread
    Hello, Petr.

    On Thu, Dec 14, 2017 at 03:27:09PM +0100, Petr Mladek wrote:
    > Ah, I know that it was me who was pessimistic about Steven's approach[1]
    > and persuaded you that offloading idea was still alive. But I am less
    > sure now.

    So, I don't really care which one gets in as long as the livelock
    problem is fixed although to my obviously partial eyes the two
    alternatives seem overly complex. That said,

    > My three main concerns about Steven's approach were:
    >
    > 1. I was afraid that it might introduce new type of deadlocks.
    >
    > But it seems that it is quite safe after all.
    >
    >
    > 2. Steven's code, implementing the hand shake, is far from trivial.
    > Few people were confused and reported false bugs.
    >
    > But the basic idea is pretty simple and straightforward. If
    > we manage to encapsulate it into few helpers, it might become
    > rather self-contained and maintainable. In each case, the needed
    > changes are much smaller than I expected.
    >
    >
    > 3. Soft-lockups are still theoretically possible with Steven's
    > approach.
    >
    > But it seems to be quite efficient in many real life scenarios,
    > including Tetsuo's stress testing. Or am I wrong?

    AFAICS, Steven's approach doesn't fix the livelock that we see quite
    often in the fleet where we don't have a safe context to keep flushing
    messages. This isn't theoretical at all. You simply don't have a
    safe context on the cpu to go to. I said I'd come back with a repro
    case but haven't had a chance to yet. I'll try to do it before the
    end of the year, but idk this is pretty obvious.

    Thanks.

    --
    tejun

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