lkml.org 
[lkml]   [2018]   [Oct]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH v2 3/3] mm, oom: hand over MMF_OOM_SKIP to exit path if it is guranteed to finish
From
Date
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.

\
 
 \ /
  Last update: 2018-10-30 10:49    [W:0.125 / U:0.300 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site