lkml.org 
[lkml]   [2007]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch] queued spinlocks (i386)
    On Thu, 29 Mar 2007, Oleg Nesterov wrote:

    > On 03/28, Nick Piggin wrote:
    > >
    > > Well with my queued spinlocks, all that lockbreak stuff can just come out
    > > of the spin_lock, break_lock out of the spinlock structure, and
    > > need_lockbreak just becomes (lock->qhead - lock->qtail > 1).
    >
    > Q: queued spinlocks are not CONFIG_PREEMPT friendly,

    Why? Is CONFIG_PREEMPT friendly to anyone? :)



    > > + asm volatile(LOCK_PREFIX "xaddw %0, %1\n\t"
    > > + : "+r" (pos), "+m" (lock->qhead) : : "memory");
    > > + while (unlikely(pos != lock->qtail))
    > > + cpu_relax();
    >
    > once we incremented lock->qhead, we have no optiion but should spin with
    > preemption disabled until pos == lock->qtail, yes?

    Yes, preemption and deterministic spinlock policies are not friends.



    - Davide


    -
    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: 2007-03-30 00:19    [W:3.501 / U:0.584 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site