linux-kernel - Re: [PATCH] mm: Add WARN_ON for possibility of infinite loop if empty lists in free_pcppages

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Message-ID: <20160819124508.GM8119@techsingularity.net>
Date:   Fri, 19 Aug 2016 13:45:08 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Pankaj Gupta <pagupta@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, vbabka@...e.cz, riel@...hat.com,
        hannes@...xchg.org, iamjoonsoo.kim@....com,
        kirill.shutemov@...ux.intel.com, izumi.taku@...fujitsu.com
Subject: Re: [PATCH] mm: Add WARN_ON for possibility of infinite loop if
 empty lists in free_pcppages_bulk'

On Fri, Aug 19, 2016 at 05:45:18PM +0530, Pankaj Gupta wrote:
> While debugging issue in realtime kernel i found a scenario
> which resulted in infinite loop resulting because of empty pcp->lists
> and valid 'to_free' value. This patch is to add 'WARN_ON' in function
> 'free_pcppages_bulk' if there is possibility of infinite loop because 
> of any bug in code.
> 

What was the bug that allowed this situation to occur? It would imply
the pcp count was somehow out of sync.

-- 
Mel Gorman
SUSE Labs