linux-kernel - Re: [PATCH] mm: don't warn about allocations which stall for too long

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Message-ID: <20171026143737.GC21147@cmpxchg.org>
Date:   Thu, 26 Oct 2017 10:37:37 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "yuwang.yuwang" <yuwang.yuwang@...baba-inc.com>
Subject: Re: [PATCH] mm: don't warn about allocations which stall for too long

On Thu, Oct 26, 2017 at 08:28:59PM +0900, Tetsuo Handa wrote:
> [...] it is possible to trigger OOM lockup and/or soft lockups when
> many threads concurrently called warn_alloc() (in order to warn
> about memory allocation stalls) due to current implementation of
> printk(), and it is difficult to obtain useful information due to
> limitation of synchronous warning approach.
>
> [...]
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Reported-by: Cong Wang <xiyou.wangcong@...il.com>
> Reported-by: yuwang.yuwang <yuwang.yuwang@...baba-inc.com>
> Reported-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Cc: Petr Mladek <pmladek@...e.com>

It would have been nice to be able to fix it instead, because there is
value in having the lockup detection. But it's true that it currently
causes more problems than it solves. Back to the drawing board for now.

Acked-by: Johannes Weiner <hannes@...xchg.org>

Thanks Tetsuo!