lkml.org 
[lkml]   [2005]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: SMP syncronization on AMD processors (broken?)
    On Thu, Oct 06, 2005 at 03:19:07PM +0200, Arjan van de Ven wrote:
    > On Thu, 2005-10-06 at 17:05 +0400, Kirill Korotaev wrote:
    > > Hello Linus, Andrew and others,
    > >
    > > Please help with a not simple question about spin_lock/spin_unlock on
    > > SMP archs. The question is whether concurrent spin_lock()'s should
    > > acquire it in more or less "fair" fashinon or one of CPUs can starve any
    > > arbitrary time while others do reacquire it in a loop.
    >
    > spinlocks are designed to not be fair. or rather are allowed to not be.
    > If you want them to be fair on x86 you need at minimum to put a
    > cpu_relax() in your busy loop...

    The question was raised exactly because cpu_relax() doesn't help on these AMD
    CPUs.

    Some Pentiums do more than expected from them, and the programs works in a
    very fair manner even without cpu_relax(), so the question boils down to
    whether there are some new AMD rules how to write such loops, is it a defect
    of the CPU, or if we are missing something else.

    Andrey
    -
    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: 2005-10-06 15:35    [W:0.034 / U:2.380 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site