linux-kernel - Re: What if a TLB flush needed to sleep?

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Message-ID: <Pine.LNX.4.64.0803261222090.31000@schroedinger.engr.sgi.com>
Date:	Wed, 26 Mar 2008 12:25:21 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	"Luck, Tony" <tony.luck@...el.com>
cc:	linux-arch@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: What if a TLB flush needed to sleep?

On Tue, 25 Mar 2008, Luck, Tony wrote:

> 2) Is it feasible to rearrange the MM code so that we don't
> hold any locks while doing a TLB flush?  Or should I implement
> some sort of spin_only_semaphore?

The EMM notifier V2 patchset contains two patches that 
convert the immap_lock and the anon_vma lock to semaphores. After that
much of the TLB flushing is (tlb_finish_mmu, tlb_gather etc) is running 
without holding any spinlocks. There would need to be additional measures 
for flushing inherent in macros (like ptep_clear_flush). Currently the 
pte functions are called under pte lock.

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