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    Subject[patch 7/7 -mm] oom: remove unnecessary code and cleanup
    Remove the redundancy in __oom_kill_task() since:

    - init can never be passed to this function: it will never be PF_EXITING
    or selectable from select_bad_process(), and

    - it will never be passed a task from oom_kill_task() without an ->mm
    and we're unconcerned about detachment from exiting tasks, there's no
    reason to protect them against SIGKILL or access to memory reserves.

    Also moves the kernel log message to a higher level since the verbosity
    is not always emitted here; we need not print an error message if an
    exiting task is given a longer timeslice.

    Signed-off-by: David Rientjes <rientjes@google.com>
    ---
    mm/oom_kill.c | 64 ++++++++++++++------------------------------------------
    1 files changed, 16 insertions(+), 48 deletions(-)

    diff --git a/mm/oom_kill.c b/mm/oom_kill.c
    --- a/mm/oom_kill.c
    +++ b/mm/oom_kill.c
    @@ -400,67 +400,35 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
    dump_tasks(mem);
    }

    -#define K(x) ((x) << (PAGE_SHIFT-10))
    -
    /*
    - * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO
    - * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO
    - * set.
    + * Give the oom killed task high priority and access to memory reserves so that
    + * it may quickly exit and free its memory.
    */
    -static void __oom_kill_task(struct task_struct *p, int verbose)
    +static void __oom_kill_task(struct task_struct *p)
    {
    - if (is_global_init(p)) {
    - WARN_ON(1);
    - printk(KERN_WARNING "tried to kill init!\n");
    - return;
    - }
    -
    - task_lock(p);
    - if (!p->mm) {
    - WARN_ON(1);
    - printk(KERN_WARNING "tried to kill an mm-less task %d (%s)!\n",
    - task_pid_nr(p), p->comm);
    - task_unlock(p);
    - return;
    - }
    -
    - if (verbose)
    - printk(KERN_ERR "Killed process %d (%s) "
    - "vsz:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
    - task_pid_nr(p), p->comm,
    - K(p->mm->total_vm),
    - K(get_mm_counter(p->mm, MM_ANONPAGES)),
    - K(get_mm_counter(p->mm, MM_FILEPAGES)));
    - task_unlock(p);
    -
    - /*
    - * We give our sacrificial lamb high priority and access to
    - * all the memory it needs. That way it should be able to
    - * exit() and clear out its resources quickly...
    - */
    p->rt.time_slice = HZ;
    set_tsk_thread_flag(p, TIF_MEMDIE);
    -
    force_sig(SIGKILL, p);
    }

    +#define K(x) ((x) << (PAGE_SHIFT-10))
    static int oom_kill_task(struct task_struct *p)
    {
    - /* WARNING: mm may not be dereferenced since we did not obtain its
    - * value from get_task_mm(p). This is OK since all we need to do is
    - * compare mm to q->mm below.
    - *
    - * Furthermore, even if mm contains a non-NULL value, p->mm may
    - * change to NULL at any time since we do not hold task_lock(p).
    - * However, this is of no concern to us.
    - */
    - if (!p->mm || p->signal->oom_adj == OOM_DISABLE)
    + task_lock(p);
    + if (!p->mm || p->signal->oom_adj == OOM_DISABLE) {
    + task_unlock(p);
    return 1;
    + }
    + pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
    + task_pid_nr(p), p->comm, K(p->mm->total_vm),
    + K(get_mm_counter(p->mm, MM_ANONPAGES)),
    + K(get_mm_counter(p->mm, MM_FILEPAGES)));
    + task_unlock(p);

    - __oom_kill_task(p, 1);
    -
    + __oom_kill_task(p);
    return 0;
    }
    +#undef K

    static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
    unsigned int points, unsigned long totalpages,
    @@ -479,7 +447,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
    * its children or threads, just set TIF_MEMDIE so it can die quickly
    */
    if (p->flags & PF_EXITING) {
    - __oom_kill_task(p, 0);
    + __oom_kill_task(p);
    return 0;
    }


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