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    SubjectRe: [PATCH 07/18] mm, proc: make clear_refs killable
    On Mon 29-02-16 18:38:45, Oleg Nesterov wrote:
    > On 02/29, Michal Hocko wrote:
    > >
    > > --- a/fs/proc/task_mmu.c
    > > +++ b/fs/proc/task_mmu.c
    > > @@ -1027,11 +1027,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
    > > };
    > >
    > > if (type == CLEAR_REFS_MM_HIWATER_RSS) {
    > > + if (down_write_killable(&mm->mmap_sem)) {
    > > + put_task_struct(task);
    > > + return -EINTR;
    > > + }
    > > +
    > > /*
    > > * Writing 5 to /proc/pid/clear_refs resets the peak
    > > * resident set size to this mm's current rss value.
    > > */
    > > - down_write(&mm->mmap_sem);
    > > reset_mm_hiwater_rss(mm);
    > > up_write(&mm->mmap_sem);
    > > goto out_mm;
    > > @@ -1043,7 +1047,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
    > > if (!(vma->vm_flags & VM_SOFTDIRTY))
    > > continue;
    > > up_read(&mm->mmap_sem);
    > > - down_write(&mm->mmap_sem);
    > > + if (down_write_killable(&mm->mmap_sem)) {
    > > + put_task_struct(task);
    > > + return -EINTR;
    > > + }
    >
    > Both lack mmput() afaics. Don't you need "goto out_mm" rather then "return" ?

    Of course I need! Thanks for catching that.

    > In this case you do not need put_task_struct().

    Why not? Both are after get_proc_task which takes a reference to the
    task...

    I will send an updated patch. Thanks!

    --
    Michal Hocko
    SUSE Labs

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