On 2018/10/30 15:31, Michal Hocko wrote: > On Tue 30-10-18 13:45:22, Tetsuo Handa wrote: >> Michal Hocko wrote: >>> @@ -3156,6 +3166,13 @@ void exit_mmap(struct mm_struct *mm) >>> vma = remove_vma(vma); >>> } >>> vm_unacct_memory(nr_accounted); >>> + >>> + /* >>> + * Now that the full address space is torn down, make sure the >>> + * OOM killer skips over this task >>> + */ >>> + if (oom) >>> + set_bit(MMF_OOM_SKIP, &mm->flags); >>> } >>> >>> /* Insert vm structure into process list sorted by address >> >> I don't like setting MMF_OOF_SKIP after remove_vma() loop. 50 users might >> call vma->vm_ops->close() from remove_vma(). Some of them are doing fs >> writeback, some of them might be doing GFP_KERNEL allocation from >> vma->vm_ops->open() with a lock also held by vma->vm_ops->close(). >> >> I don't think that waiting for completion of remove_vma() loop is safe. > > What do you mean by 'safe' here? >
safe = "Does not cause OOM lockup." remove_vma() is allowed to sleep, and some users might depend on memory allocation when the OOM killer is waiting for remove_vma() to complete.
