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From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>,
	Linux-MM <linux-mm@kvack.org>,
	Linux-RT-Users <linux-rt-users@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Chuck Lever <chuck.lever@oracle.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 08/11] mm/page_alloc: Explicitly acquire the zone lock in __free_pages_ok
Date: Thu, 15 Apr 2021 12:24:14 +0200
Message-ID: <1f6fbbaa-bd0e-3e04-26d5-d8f6aee6bd1d@suse.cz> (raw)
In-Reply-To: <20210414133931.4555-9-mgorman@techsingularity.net>

On 4/14/21 3:39 PM, Mel Gorman wrote:
> __free_pages_ok() disables IRQs before calling a common helper
> free_one_page() that acquires the zone lock. This is not safe according
> to Documentation/locking/locktypes.rst and in this context, IRQ disabling
> is not protecting a per_cpu_pages structure either or a local_lock would
> be used.
> 
> This patch explicitly acquires the lock with spin_lock_irqsave instead of
> relying on a helper. This removes the last instance of local_irq_save()
> in page_alloc.c.

\o/

> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/page_alloc.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 1ed370668e7f..6791e9361076 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1559,21 +1559,18 @@ static void __free_pages_ok(struct page *page, unsigned int order,
>  	unsigned long flags;
>  	int migratetype;
>  	unsigned long pfn = page_to_pfn(page);
> +	struct zone *zone = page_zone(page);
>  
>  	if (!free_pages_prepare(page, order, true))
>  		return;
>  
>  	migratetype = get_pfnblock_migratetype(page, pfn);
>  
> -	/*
> -	 * TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock
> -	 * and protect vmstat updates.
> -	 */
> -	local_irq_save(flags);
> +	spin_lock_irqsave(&zone->lock, flags);
>  	__count_vm_events(PGFREE, 1 << order);
> -	free_one_page(page_zone(page), page, pfn, order, migratetype,
> -		      fpi_flags);
> -	local_irq_restore(flags);
> +	migratetype = check_migratetype_isolated(zone, page, pfn, migratetype);
> +	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
> +	spin_unlock_irqrestore(&zone->lock, flags);
>  }
>  
>  void __free_pages_core(struct page *page, unsigned int order)
> 


  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-14 13:39 [PATCH 0/11 v3] Use local_lock for pcp protection and reduce stat overhead Mel Gorman
2021-04-14 13:39 ` [PATCH 01/11] mm/page_alloc: Split per cpu page lists and zone stats Mel Gorman
2021-04-14 13:39 ` [PATCH 02/11] mm/page_alloc: Convert per-cpu list protection to local_lock Mel Gorman
2021-04-14 13:39 ` [PATCH 03/11] mm/vmstat: Convert NUMA statistics to basic NUMA counters Mel Gorman
2021-04-14 13:39 ` [PATCH 04/11] mm/vmstat: Inline NUMA event counter updates Mel Gorman
2021-04-14 16:20   ` Vlastimil Babka
2021-04-14 16:26     ` Vlastimil Babka
2021-04-15  9:34       ` Mel Gorman
2021-04-14 13:39 ` [PATCH 05/11] mm/page_alloc: Batch the accounting updates in the bulk allocator Mel Gorman
2021-04-14 16:31   ` Vlastimil Babka
2021-04-14 13:39 ` [PATCH 06/11] mm/page_alloc: Reduce duration that IRQs are disabled for VM counters Mel Gorman
2021-04-14 17:10   ` Vlastimil Babka
2021-04-14 13:39 ` [PATCH 07/11] mm/page_alloc: Remove duplicate checks if migratetype should be isolated Mel Gorman
2021-04-14 17:21   ` Vlastimil Babka
2021-04-15  9:33     ` Mel Gorman
2021-04-15 11:24       ` Vlastimil Babka
2021-04-14 13:39 ` [PATCH 08/11] mm/page_alloc: Explicitly acquire the zone lock in __free_pages_ok Mel Gorman
2021-04-15 10:24   ` Vlastimil Babka [this message]
2021-04-14 13:39 ` [PATCH 09/11] mm/page_alloc: Avoid conflating IRQs disabled with zone->lock Mel Gorman
2021-04-15 12:25   ` Vlastimil Babka
2021-04-15 14:11     ` Mel Gorman
2021-04-14 13:39 ` [PATCH 10/11] mm/page_alloc: Update PGFREE outside the zone lock in __free_pages_ok Mel Gorman
2021-04-15 13:04   ` Vlastimil Babka
2021-04-14 13:39 ` [PATCH 11/11] mm/page_alloc: Embed per_cpu_pages locking within the per-cpu structure Mel Gorman
2021-04-15 14:53   ` Vlastimil Babka
2021-04-15 15:29     ` Mel Gorman

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