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Re: [PATCH 07/18] mm, proc: make clear_refs killable

From Michal Hocko <mhocko@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH 07/18] mm, proc: make clear_refs killable
Date 2016-02-29 19:00 +0100
Message-ID <r7AgW-6as-5@gated-at.bofh.it> (permalink)
References <r7w3D-3yu-3@gated-at.bofh.it> <r7w3E-3yu-9@gated-at.bofh.it> <r7zXA-63L-5@gated-at.bofh.it>
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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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Thread

[PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-02-29 14:30 +0100
  Re: [PATCH 07/18] mm, proc: make clear_refs killable kbuild test robot <lkp@intel.com> - 2016-02-29 14:50 +0100
  Re: [PATCH 07/18] mm, proc: make clear_refs killable Oleg Nesterov <oleg@redhat.com> - 2016-02-29 18:40 +0100
    Re: [PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-02-29 19:00 +0100
      Re: [PATCH 07/18] mm, proc: make clear_refs killable Oleg Nesterov <oleg@redhat.com> - 2016-02-29 19:00 +0100
        Re: [PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-02-29 19:10 +0100
  [PATCH] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-02-29 19:10 +0100
    Re: [PATCH] mm, proc: make clear_refs killable Oleg Nesterov <oleg@redhat.com> - 2016-02-29 19:20 +0100
    Re: [PATCH] mm, proc: make clear_refs killable kbuild test robot <lkp@intel.com> - 2016-02-29 21:30 +0100

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