[lkml]   [2008]   [Feb]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep

    On Fri, 2008-02-22 at 08:35 -0500, Steven Rostedt wrote:

    > > My assumption is that the xchg() (inside update_current()) acts as an
    > > effective wmb(). If xchg() does not have this property, then this code
    > > is broken and patch 6/14 should also add a:
    > >
    > >
    > > + smp_wmb();
    > I believe that the wmb would be needed. I doubt that xchg on all archs
    > would force any ordering of reads and writes. It only needs to guarantee the
    > atomic nature of the data exchange. I don't see any reason that it would
    > imply any type of memory barrier.

    Documentation/memory-barriers.txt states:

    Any atomic operation that modifies some state in memory and returns information
    about the state (old or new) implies an SMP-conditional general memory barrier
    (smp_mb()) on each side of the actual operation (with the exception of
    explicit lock operations, described later). These include:


     \ /
      Last update: 2008-02-22 14:45    [W:0.020 / U:2.076 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site