Hi Michal,

[auto build test ERROR on mmotm/master]
[also build test ERROR on v4.13-rc2 next-20170724]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:    
https://github.com/0day-ci/linux/commits/Michal-Hocko/mm-oom-allow-oom-reaper-to-race-with-exit_mmap/20170724-233159
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: x86_64-randconfig-x016-201730 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All error/warnings (new ones prefixed by >>):

   mm/oom_kill.c: In function '__oom_reap_task_mm':
>> mm/oom_kill.c:523:9: error: 'ret' undeclared (first use in this function)
     return ret;
            ^~~
   mm/oom_kill.c:523:9: note: each undeclared identifier is reported only once 
for each function it appears in
>> mm/oom_kill.c:524:1: warning: control reaches end of non-void function 
>> [-Wreturn-type]
    }
    ^

vim +/ret +523 mm/oom_kill.c

03049269d Michal Hocko       2016-03-25  468  
7ebffa455 Tetsuo Handa       2016-10-07  469  static bool 
__oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
aac453635 Michal Hocko       2016-03-25  470  {
aac453635 Michal Hocko       2016-03-25  471    struct mmu_gather tlb;
aac453635 Michal Hocko       2016-03-25  472    struct vm_area_struct *vma;
e2fe14564 Michal Hocko       2016-05-27  473  
aac453635 Michal Hocko       2016-03-25  474    if 
(!down_read_trylock(&mm->mmap_sem)) {
fa60da35c Andrew Morton      2017-07-14  475            
trace_skip_task_reaping(tsk->pid);
ed7a155c6 Michal Hocko       2017-07-24  476            return false;
e5e3f4c4f Michal Hocko       2016-07-26  477    }
e5e3f4c4f Michal Hocko       2016-07-26  478  
ed7a155c6 Michal Hocko       2017-07-24  479    /* There is nothing to reap so 
bail out without signs in the log */
ed7a155c6 Michal Hocko       2017-07-24  480    if (!mm->mmap)
ed7a155c6 Michal Hocko       2017-07-24  481            goto unlock;
aac453635 Michal Hocko       2016-03-25  482  
fa60da35c Andrew Morton      2017-07-14  483    
trace_start_task_reaping(tsk->pid);
fa60da35c Andrew Morton      2017-07-14  484  
3f70dc38c Michal Hocko       2016-10-07  485    /*
3f70dc38c Michal Hocko       2016-10-07  486     * Tell all users of 
get_user/copy_from_user etc... that the content
3f70dc38c Michal Hocko       2016-10-07  487     * is no longer stable. No 
barriers really needed because unmapping
3f70dc38c Michal Hocko       2016-10-07  488     * should imply barriers 
already and the reader would hit a page fault
3f70dc38c Michal Hocko       2016-10-07  489     * if it stumbled over a reaped 
memory.
3f70dc38c Michal Hocko       2016-10-07  490     */
3f70dc38c Michal Hocko       2016-10-07  491    set_bit(MMF_UNSTABLE, 
&mm->flags);
3f70dc38c Michal Hocko       2016-10-07  492  
aac453635 Michal Hocko       2016-03-25  493    tlb_gather_mmu(&tlb, mm, 0, -1);
aac453635 Michal Hocko       2016-03-25  494    for (vma = mm->mmap ; vma; vma 
= vma->vm_next) {
235190738 Kirill A. Shutemov 2017-02-22  495            if 
(!can_madv_dontneed_vma(vma))
aac453635 Michal Hocko       2016-03-25  496                    continue;
aac453635 Michal Hocko       2016-03-25  497  
aac453635 Michal Hocko       2016-03-25  498            /*
aac453635 Michal Hocko       2016-03-25  499             * Only anonymous pages 
have a good chance to be dropped
aac453635 Michal Hocko       2016-03-25  500             * without additional 
steps which we cannot afford as we
aac453635 Michal Hocko       2016-03-25  501             * are OOM already.
aac453635 Michal Hocko       2016-03-25  502             *
aac453635 Michal Hocko       2016-03-25  503             * We do not even care 
about fs backed pages because all
aac453635 Michal Hocko       2016-03-25  504             * which are 
reclaimable have already been reclaimed and
aac453635 Michal Hocko       2016-03-25  505             * we do not want to 
block exit_mmap by keeping mm ref
aac453635 Michal Hocko       2016-03-25  506             * count elevated 
without a good reason.
aac453635 Michal Hocko       2016-03-25  507             */
aac453635 Michal Hocko       2016-03-25  508            if 
(vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
aac453635 Michal Hocko       2016-03-25  509                    
unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
3e8715fdc Kirill A. Shutemov 2017-02-22  510                                    
 NULL);
aac453635 Michal Hocko       2016-03-25  511    }
aac453635 Michal Hocko       2016-03-25  512    tlb_finish_mmu(&tlb, 0, -1);
bc448e897 Michal Hocko       2016-03-25  513    pr_info("oom_reaper: reaped 
process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
bc448e897 Michal Hocko       2016-03-25  514                    
task_pid_nr(tsk), tsk->comm,
bc448e897 Michal Hocko       2016-03-25  515                    
K(get_mm_counter(mm, MM_ANONPAGES)),
bc448e897 Michal Hocko       2016-03-25  516                    
K(get_mm_counter(mm, MM_FILEPAGES)),
bc448e897 Michal Hocko       2016-03-25  517                    
K(get_mm_counter(mm, MM_SHMEMPAGES)));
36324a990 Michal Hocko       2016-03-25  518  
fa60da35c Andrew Morton      2017-07-14  519    
trace_finish_task_reaping(tsk->pid);
ed7a155c6 Michal Hocko       2017-07-24  520  unlock:
ed7a155c6 Michal Hocko       2017-07-24  521    up_read(&mm->mmap_sem);
ed7a155c6 Michal Hocko       2017-07-24  522  
aac453635 Michal Hocko       2016-03-25 @523    return ret;
aac453635 Michal Hocko       2016-03-25 @524  }
aac453635 Michal Hocko       2016-03-25  525  

:::::: The code at line 523 was first introduced by commit
:::::: aac453635549699c13a84ea1456d5b0e574ef855 mm, oom: introduce oom reaper

:::::: TO: Michal Hocko <mho...@suse.com>
:::::: CC: Linus Torvalds <torva...@linux-foundation.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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