lkml.org 
[lkml]   [2009]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH -v9][RFC] mutex: implement adaptive spinning


    On Tue, 13 Jan 2009, Peter Zijlstra wrote:
    >
    > Change mutex contention behaviour such that it will sometimes busy wait on
    > acquisition - moving its behaviour closer to that of spinlocks.

    Okey, dokey. Looks reasonable, but I wonder if this part came from v8 and
    wasn't intentional:

    > + if (atomic_xchg(&lock->count, -1) == 1) {
    > + lock_acquired(&lock->dep_map, ip);
    > + mutex_set_owner(lock);
    > + preempt_enable();
    > + return 0;
    > + }

    Now you're forcing the slow-path on unlock. Maybe it was intentional,
    maybe it wasn't. Did you perhaps mean

    if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {

    here? I thought we agreed it was safe, if only because it should be
    equivalent to just having done "mutex_trylock()" instead of a "real" lock
    sequence.

    Linus


    \
     
     \ /
      Last update: 2009-01-13 17:19    [W:0.022 / U:10.164 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site