lkml.org 
[lkml]   [2011]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 06/16] freezer: make exiting tasks properly unfreezable
    Date
    There's no point in freezing an exiting task.  The current code
    seemingly tries that by calling clear_freeze_flag() from exit_mm() but
    it's racy as freeze might happen afterwards.

    This patch removes the racy clear_freeze_flag() makes do_exit() set
    PF_NOFREEZE after PTRACE_EVENT_EXIT, after which freezing doesn't make
    sense.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    kernel/exit.c | 8 ++++++--
    kernel/power/process.c | 3 +--
    2 files changed, 7 insertions(+), 4 deletions(-)

    diff --git a/kernel/exit.c b/kernel/exit.c
    index 2913b35..ac58259 100644
    --- a/kernel/exit.c
    +++ b/kernel/exit.c
    @@ -679,8 +679,6 @@ static void exit_mm(struct task_struct * tsk)
    tsk->mm = NULL;
    up_read(&mm->mmap_sem);
    enter_lazy_tlb(mm, current);
    - /* We don't want this task to be frozen prematurely */
    - clear_freeze_flag(tsk);
    if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
    atomic_dec(&mm->oom_disable_count);
    task_unlock(tsk);
    @@ -915,6 +913,12 @@ NORET_TYPE void do_exit(long code)

    ptrace_event(PTRACE_EVENT_EXIT, code);

    + /*
    + * With ptrace notification done, there's no point in freezing from
    + * here on. Disallow freezing.
    + */
    + current->flags |= PF_NOFREEZE;
    +
    validate_creds_for_do_exit(tsk);

    /*
    diff --git a/kernel/power/process.c b/kernel/power/process.c
    index bec09c3..ddfaba4 100644
    --- a/kernel/power/process.c
    +++ b/kernel/power/process.c
    @@ -25,8 +25,7 @@
    static inline int freezable(struct task_struct * p)
    {
    if ((p == current) ||
    - (p->flags & PF_NOFREEZE) ||
    - (p->exit_state != 0))
    + (p->flags & PF_NOFREEZE))
    return 0;
    return 1;
    }
    --
    1.7.6


    \
     
     \ /
      Last update: 2011-08-19 16:21    [W:0.031 / U:29.764 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site