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SubjectRe: possible deadlock in __wake_up_common_lock
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On 2019/01/03 3:19, Qian Cai wrote:
> On 1/2/19 1:06 PM, Mel Gorman wrote:
>
>> While I recognise there is no test case available, how often does this
>> trigger in syzbot as it would be nice to have some confirmation any
>> patch is really fixing the problem.
>
> I think I did manage to trigger this every time running a mmap() workload
> causing swapping and a low-memory situation [1].
>
> [1]
> https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/oom/oom01.c

wakeup_kswapd() is called because tlb_next_batch() is doing GFP_NOWAIT
allocation. But since tlb_next_batch() can tolerate allocation failure,
does below change in tlb_next_batch() help?

#define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM)

- batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
+ batch = (void *)__get_free_pages(__GFP_NOWARN, 0);

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