lkml.org 
[lkml]   [2004]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [patch] voluntary-preempt-2.6.8-rc4-O7

    * Lee Revell <rlrevell@joe-job.com> wrote:

    > In some of the traces, like this one:
    >
    > http://krustophenia.net/testresults.php?dataset=2.6.8-rc4-bk3-O7#/var/www/2.6.8-rc4-bk3-O7/mount_reiserfs_latency_trace.txt
    >
    > there are calls to voluntary_resched. How is this possible? Does it
    > mean that we called voluntary_resched while holding a spinlock, where
    > we needed to call voluntary_preempt_lock(&foo_lock), and thus failed
    > to reschedule?

    voluntary_resched() was probably called as part of the might_sleep_if()
    done in mm/slab.c. If you have CONFIG_DEBUG_SPINLOCK_SLEEP enabled then
    the kernel should have complained about 'Debug: sleeping function ...'.

    but what i think happened here is that reiserfs still uses
    lock_kernel()/unlock_kernel() quite alot (eg. ext3 or xfs doesnt), which
    from a preemptability POV is just as much of a critical section as a
    spinlock, but processes can sleep (the scheduler auto-releases and
    auto-reacquires the big kernel lock).

    Ingo

    --- linux/kernel/sched.c.orig
    +++ linux/kernel/sched.c
    @@ -3210,11 +3210,11 @@ __setup("voluntary-preempt=", voluntary_

    int __sched voluntary_resched(void)
    {
    - if (kernel_preemption || !voluntary_preemption)
    - return 0;
    #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
    __might_sleep(__FILE__, __LINE__);
    #endif
    + if (kernel_preemption || !voluntary_preemption)
    + return 0;
    /*
    * The system_state check is somewhat ugly but we might be
    * called during early boot when we are not yet ready to reschedule.
    -
    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: 2005-03-22 14:05    [W:0.027 / U:146.184 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site