linux-kernel - Re: Sleeping BUG in khugepaged for i586

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Message-ID: <alpine.DEB.2.10.1706091537020.66176@chino.kir.corp.google.com>
Date:   Fri, 9 Jun 2017 15:38:44 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Larry Finger <Larry.Finger@...inger.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Sleeping BUG in khugepaged for i586

On Thu, 8 Jun 2017, Michal Hocko wrote:

> I would just pull the cond_resched out of __collapse_huge_page_copy
> right after pte_unmap. But I am not really sure why this cond_resched is
> really needed because the changelog of the patch which adds is is quite
> terse on details.

I'm not sure what could possibly be added to the changelog.  We have 
encountered need_resched warnings during the iteration.  We fix these 
because need_resched warnings suppress future warnings of the same type 
for issues that are more important.

I can fix the i386 issue but removing the cond_resched() entirely isn't 
really suitable.