Date: Tue, 15 Nov 2005 10:22:06 -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
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On Tue, 15 Nov 2005, Andrew Morton wrote:

> But lru_add_drain_per_cpu() will be called from interrupt context: the IPI
> handler.

Ahh.. thought you meant the lru_add_drain run on the local processor.
 
> I'm asking whether it is safe for the IPI handler to reenable interupts on
> all architectures.  It might be so, but I don't recall ever having seen it
> discussed, nor have I seen code which does it.

smp_call_function is also used by the slab allocator to drain the 
pages. All the spinlocks in there and those of the page allocator (called 
for freeing pages) use spin_lock_irqsave. Why is this not used for 
lru_add_drain() and friends?

Maybe we need to start a new thread so that others see it?

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