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Message-ID: <530f88a1-3aa1-c36f-f487-7e5e33402fb0@I-love.SAKURA.ne.jp>
Date: Thu, 3 Jan 2019 10:28:45 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Qian Cai <cai@....pw>, Mel Gorman <mgorman@...hsingularity.net>,
Vlastimil Babka <vbabka@...e.cz>
Cc: syzbot <syzbot+93d94a001cfbce9e60e1@...kaller.appspotmail.com>,
aarcange@...hat.com, akpm@...ux-foundation.org,
kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux@...inikbrodowski.net, mhocko@...e.com,
rientjes@...gle.com, syzkaller-bugs@...glegroups.com,
xieyisheng1@...wei.com, zhongjiang@...wei.com,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>
Subject: Re: possible deadlock in __wake_up_common_lock
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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