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    SubjectRe: [patch] increase spinlock-debug looping timeouts from 1 sec to 1 min

    * Andrew Morton <> wrote:

    > OK. That sucks. A sufficiently large machine with the right mix of
    > latencies will get hit by the NMI watchdog in write_lock_irq().
    > But presumably the situation is much worse with CONFIG_DEBUG_SPINLOCK
    > because of that __delay().
    > So how about we remove the __delay() (which is wrong anyway, because
    > loops_per_jiffy isn't calculated with a write_trylock() in the loop
    > (which means we're getting scarily close to the NMI watchdog at
    > present)).
    > Instead, calculate a custom loops_per_jiffy for this purpose in
    > lib/spinlock_debug.c?

    hm, that would be yet another calibration loop with the potential to be
    wrong (and which would slow down the bootup process). If loops_per_jiffy
    is wrong then our timings are toast anyway.

    I think increasing the timeout to 60 secs ought to be enough - 1 sec was
    a bit too close to valid delays and i can imagine really high loads
    causing 1 sec delays (especially if something like SysRq-T is holding
    the tasklist_lock for long).

    The write_trylock + __delay in the loop is not a problem or a bug, as
    the trylock will at most _increase_ the delay - and our goal is to not
    have a false positive, not to be absolutely accurate about the
    measurement here.

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      Last update: 2006-06-19 10:42    [W:0.029 / U:33.824 seconds]
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