[lkml]   [2010]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Subject[PATCH 0/6] sched/cpusets fixes, more changes are needed
    Ingo, Peter.

    Unless I missed something, with or without these patches the TASK_WAKING
    logic in do_fork() is very broken.

    - do_fork() clears PF_STARTING and then calls wake_up_new_task()
    which finally does s/WAKING/RUNNING.

    But. Nobody can take rq->lock in between. This means a signal
    from irq (quite possible with CLONE_THREAD) or another rt
    thread which preempts us can lockup.

    - the comment in wake_up_new_task says:

    We still have TASK_WAKING but PF_STARTING is gone now, meaning
    ->cpus_allowed is stable

    this is not true. Yes, nobody can take rq->lock _after_ we cleared
    PF_STARTING, but it is possible that another thread took this lock
    before and still holds it doing, say, sched_setaffinity().


    If yes. I can make a patch, but the question is: what is the point to use
    TASK_WAKING in fork pathes? Can't sched_fork() set TASK_RUNNING instead?
    Afaics, TASK_RUNNING can equally protect from premature wakeups but doesn't
    these PF_STARTING complications.

    As for this series. Please review. I don't understand how it is possible
    to really test these changes.

    Dear cpuset developers! Please review ;) If you don't like 6/6, please make
    a better fix. I tried to make as "simple" patch as possible because I hardly
    understand cpuset.c, last time I quickly read it a long ago.


     \ /
      Last update: 2010-03-15 10:15    [W:0.019 / U:60.816 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site