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    Subject[PATCH 1/6] sys_times: don't take tasklist_lock
    sys_times: dont' take tasklist_lock

    Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

    --- 2.6.16-rc3/kernel/sys.c~ Thu Feb 23 00:27:27 2006
    +++ 2.6.16-rc3/kernel/sys.c Thu Feb 23 00:28:24 2006
    @@ -1018,7 +1018,7 @@ asmlinkage long sys_times(struct tms __u
    struct task_struct *t;
    cputime_t utime, stime, cutime, cstime;

    - read_lock(&tasklist_lock);
    + spin_lock_irq(&tsk->sighand->siglock);
    utime = tsk->signal->utime;
    stime = tsk->signal->stime;
    t = tsk;
    @@ -1028,20 +1028,9 @@ asmlinkage long sys_times(struct tms __u
    t = next_thread(t);
    } while (t != tsk);

    - /*
    - * While we have tasklist_lock read-locked, no dying thread
    - * can be updating current->signal->[us]time. Instead,
    - * we got their counts included in the live thread loop.
    - * However, another thread can come in right now and
    - * do a wait call that updates current->signal->c[us]time.
    - * To make sure we always see that pair updated atomically,
    - * we take the siglock around fetching them.
    - */
    - spin_lock_irq(&tsk->sighand->siglock);
    cutime = tsk->signal->cutime;
    cstime = tsk->signal->cstime;
    spin_unlock_irq(&tsk->sighand->siglock);
    - read_unlock(&tasklist_lock);

    tmp.tms_utime = cputime_to_clock_t(utime);
    tmp.tms_stime = cputime_to_clock_t(stime);
    -
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