lkml.org 
[lkml]   [2012]   [Jun]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC patch 2/5] smpboot: Provide infrastructure for percpu hotplug threads
    On Wed, 13 Jun 2012, Paul E. McKenney wrote:
    > On Wed, Jun 13, 2012 at 11:00:54AM -0000, Thomas Gleixner wrote:
    >
    > So I am currently trying to apply this to RCU's per-CPU kthread.
    > I don't believe that I need to mess with RCU's per-rcu_node kthread
    > because it can just have its affinity adjusted when the first CPU
    > onlines and the last CPU offlines for the corresponding rcu_node.
    >
    > One question below about the order of parking.
    >
    > Also, I have not yet figured out how this avoids a parked thread waking
    > up while the CPU is offline, but I am probably still missing something.

    If it's just a spurious wakeup then it goes back to sleep right away
    as nothing cleared the park bit.

    If something calls unpark(), then it's toast. I should put a warning
    into the code somewhere to catch that case.

    > > +void smpboot_park_threads(unsigned int cpu)
    > > +{
    > > + struct smp_hotplug_thread *cur;
    > > +
    > > + mutex_lock(&smpboot_threads_lock);
    > > + list_for_each_entry(cur, &hotplug_threads, list)
    >
    > Shouldn't this be list_for_each_entry_reverse()? Yes, the notifiers
    > still run in the same order for both online and offline, but all uses
    > of smpboot_park_threads() would be new, so should be OK with the
    > proper ordering, right?

    Duh, yes

    Thanks,

    tglx


    \
     
     \ /
      Last update: 2012-06-13 21:41    [W:2.307 / U:0.036 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site