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    Subject[PATCH 3/5] oom: Fix child process iteration properly
    Date
    Oleg pointed out that current oom child process iterating logic is wrong.

    > list_for_each_entry(p->children) can only see the tasks forked
    > by p, it can't see other children forked by its sub-threads.

    This patch fixes it.

    Reported-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    ---
    mm/oom_kill.c | 34 ++++++++++++++++++++--------------
    1 files changed, 20 insertions(+), 14 deletions(-)

    diff --git a/mm/oom_kill.c b/mm/oom_kill.c
    index 70e1a85..1bdf27d 100644
    --- a/mm/oom_kill.c
    +++ b/mm/oom_kill.c
    @@ -88,6 +88,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
    {
    unsigned long points, cpu_time, run_time;
    struct task_struct *c;
    + struct task_struct *t = p;
    struct task_struct *child;
    int oom_adj = p->signal->oom_adj;
    struct task_cputime task_time;
    @@ -125,14 +126,16 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
    * child is eating the vast majority of memory, adding only half
    * to the parents will make the child our kill candidate of choice.
    */
    - list_for_each_entry(c, &p->children, sibling) {
    - child = find_lock_task_mm(c);
    - if (child) {
    - if (child->mm != p->mm)
    - points += child->mm->total_vm/2 + 1;
    - task_unlock(child);
    + do {
    + list_for_each_entry(c, &t->children, sibling) {
    + child = find_lock_task_mm(c);
    + if (child) {
    + if (child->mm != p->mm)
    + points += child->mm->total_vm/2 + 1;
    + task_unlock(child);
    + }
    }
    - }
    + } while_each_thread(p, t);

    /*
    * CPU time is in tens of seconds and run time is in thousands
    @@ -432,6 +435,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
    const char *message)
    {
    struct task_struct *c;
    + struct task_struct *t = p;

    if (printk_ratelimit())
    dump_header(p, gfp_mask, order, mem);
    @@ -449,14 +453,16 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
    message, task_pid_nr(p), p->comm, points);

    /* Try to kill a child first */
    - list_for_each_entry(c, &p->children, sibling) {
    - if (c->mm == p->mm)
    - continue;
    + do {
    + list_for_each_entry(c, &t->children, sibling) {
    + if (c->mm == p->mm)
    + continue;

    - /* Ok, Kill the child */
    - if (!__oom_kill_process(c, mem, 1))
    - return 0;
    - }
    + /* Ok, Kill the child */
    + if (!__oom_kill_process(c, mem, 1))
    + return 0;
    + }
    + } while_each_thread(p, t);

    return __oom_kill_process(p, mem, 1);
    }
    --
    1.6.5.2




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