linux-kernel - Re: [PATCH][RFC v2] PM / Hibernate: Disable wathdog when creating snapshot

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Message-ID: <20170816123359.GC32161@dhcp22.suse.cz>
Date:   Wed, 16 Aug 2017 14:33:59 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC v2] PM / Hibernate: Disable wathdog when creating
 snapshot

On Wed 16-08-17 12:53:38, Chen Yu wrote:
[...]
> @@ -2537,10 +2538,15 @@ void mark_free_pages(struct zone *zone)
>  	unsigned long flags;
>  	unsigned int order, t;
>  	struct page *page;
> +	bool wd_suspended;
>  
>  	if (zone_is_empty(zone))
>  		return;
>  
> +	wd_suspended = lockup_detector_suspend() ? false : true;
> +	if (!wd_suspended)
> +		pr_warn_once("Failed to disable lockup detector during hibernation.\n");
> +
>  	spin_lock_irqsave(&zone->lock, flags);
>  
>  	max_zone_pfn = zone_end_pfn(zone);

I am not maintainer of this code so I am not very familiar with the full
context of this function but lockup_detector_suspend is just too heavy
for the purpose you are trying to achive. Really why don't you just
poke the watchdog every N pages?
-- 
Michal Hocko
SUSE Labs