lkml.org 
[lkml]   [2006]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch] increase spinlock-debug looping timeouts from 1 sec to 1 min

    * Andrew Morton <akpm@osdl.org> 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.

    Ingo
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-06-19 10:42    [W:0.022 / U:0.484 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site