lkml.org 
[lkml]   [2009]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch 3/21] x86, bts: wait until traced task has been scheduled out

    * Metzger, Markus T <markus.t.metzger@intel.com> wrote:

    > >-----Original Message-----
    > >From: Ingo Molnar [mailto:mingo@elte.hu]
    > >Sent: Wednesday, April 01, 2009 1:42 PM
    > >To: Oleg Nesterov; Peter Zijlstra
    >
    >
    > >* Oleg Nesterov <oleg@redhat.com> wrote:
    > >
    > >> On 03/31, Markus Metzger wrote:
    > >> >
    > >> > +static void wait_to_unschedule(struct task_struct *task)
    > >> > +{
    > >> > + unsigned long nvcsw;
    > >> > + unsigned long nivcsw;
    > >> > +
    > >> > + if (!task)
    > >> > + return;
    > >> > +
    > >> > + if (task == current)
    > >> > + return;
    > >> > +
    > >> > + nvcsw = task->nvcsw;
    > >> > + nivcsw = task->nivcsw;
    > >> > + for (;;) {
    > >> > + if (!task_is_running(task))
    > >> > + break;
    > >> > + /*
    > >> > + * The switch count is incremented before the actual
    > >> > + * context switch. We thus wait for two switches to be
    > >> > + * sure at least one completed.
    > >> > + */
    > >> > + if ((task->nvcsw - nvcsw) > 1)
    > >> > + break;
    > >> > + if ((task->nivcsw - nivcsw) > 1)
    > >> > + break;
    > >> > +
    > >> > + schedule();
    > >>
    > >> schedule() is a nop here. We can wait unpredictably long...
    > >>
    > >> Ingo, do have have any ideas to improve this helper?
    > >
    > >hm, there's a similar looking existing facility:
    > >wait_task_inactive(). Have i missed some subtle detail that makes it
    > >inappropriate for use here?
    >
    > wait_task_inactive() waits until the task is no longer
    > TASK_RUNNING.

    No, that's wrong, wait_task_inactive() waits until the task
    deschedules.

    Ingo


    \
     
     \ /
      Last update: 2009-04-01 14:55    [W:0.032 / U:32.688 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site