Date: Tue, 15 Nov 2005 08:38:21 -0800 (PST)
From: Christoph Lameter <clameter@engr.sgi.com>
To: Andrew Morton <akpm@osdl.org>
cc: torvalds@osdl.org, marcelo.tosatti@cyclades.com, kravetz@us.ibm.com,
       raybry@mpdtxmail.amd.com, lee.schermerhorn@hp.com,
       linux-kernel@vger.kernel.org, magnus.damm@gmail.com, pj@sgi.com,
       haveblue@us.ibm.com, kamezawa.hiroyu@jp.fujitsu.com
Subject: Re: [PATCH 1/5] Swap Migration V5: LRU operations
In-Reply-To: <20051114214415.1e107c7b.akpm@osdl.org>
Message-ID: <Pine.LNX.4.62.0511150837190.9258@schroedinger.engr.sgi.com>
References: <20051101031239.12488.76816.sendpatchset@schroedinger.engr.sgi.com>
 <20051101031244.12488.38211.sendpatchset@schroedinger.engr.sgi.com>
 <20051114214415.1e107c7b.akpm@osdl.org>
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On Mon, 14 Nov 2005, Andrew Morton wrote:

> >  +int isolate_lru_page(struct page *page)
> >  +{
> >  +	int rc = 0;
> >  +	struct zone *zone = page_zone(page);
> >  +
> >  +redo:
> >  +	spin_lock_irq(&zone->lru_lock);
> >  +	rc = __isolate_lru_page(zone, page);
> >  +	spin_unlock_irq(&zone->lru_lock);
> >  +	if (rc == 0) {
> >  +		/*
> >  +		 * Maybe this page is still waiting for a cpu to drain it
> >  +		 * from one of the lru lists?
> >  +		 */
> >  +		smp_call_function(&lru_add_drain_per_cpu, NULL, 0 , 1);
> 
> lru_add_drain() ends up doing spin_unlock_irq(), so we'll enable interrupts
> within the smp_call_function() handler.  Is that legal on all
> architectures?

isolate_lru_pages() is only called within a process context in the swap 
migration patches. The hotplug folks may have to address this if they want 
to isolate pages from interrupts etc.

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