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Date:   Mon, 17 Jun 2019 09:53:57 +0300
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     "Alastair D'Silva" <alastair@au1.ibm.com>
Cc:     alastair@d-silva.org, Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Oscar Salvador <osalvador@suse.com>,
        Michal Hocko <mhocko@suse.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Wei Yang <richard.weiyang@gmail.com>,
        Juergen Gross <jgross@suse.com>, Qian Cai <cai@lca.pw>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jiri Kosina <jkosina@suse.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Mukesh Ojha <mojha@codeaurora.org>,
        Arun KS <arunks@codeaurora.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Baoquan He <bhe@redhat.com>,
        Logan Gunthorpe <logang@deltatee.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] mm/hotplug: Avoid RCU stalls when removing large
 amounts of memory
References: <20190617043635.13201-1-alastair@au1.ibm.com>
 <20190617043635.13201-5-alastair@au1.ibm.com>
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On Mon, Jun 17, 2019 at 02:36:30PM +1000, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@d-silva.org>
> 
> When removing sufficiently large amounts of memory, we trigger RCU stall
> detection. By periodically calling cond_resched(), we avoid bogus stall
> warnings.
> 
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> ---
>  mm/memory_hotplug.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index e096c987d261..382b3a0c9333 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -578,6 +578,9 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
>  		__remove_section(zone, __pfn_to_section(pfn), map_offset,
>  				 altmap);
>  		map_offset = 0;
> +
> +		if (!(i & 0x0FFF))

No magic numbers please. And a comment would be appreciated.

> +			cond_resched();
>  	}
> 
>  	set_zone_contiguous(zone);
> -- 
> 2.21.0
> 

-- 
Sincerely yours,
Mike.