linux-kernel - Re: [PATCH] xen: use spin_lock_nest

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Message-ID: <20081009122549.GA2952@elte.hu>
Date:	Thu, 9 Oct 2008 14:25:49 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xen: use spin_lock_nest_lock when pinning a pagetable


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> When pinning/unpinning a pagetable with split pte locks, we can end up
> holding multiple pte locks at once (we need to hold the locks while
> there's a pending batched hypercall affecting the pte page).  Because
> all the pte locks are in the same lock class, lockdep thinks that
> we're potentially taking a lock recursively.
>
> This warning is spurious because we always take the pte locks while
> holding mm->page_table_lock.  lockdep now has spin_lock_nest_lock to
> express this kind of dominant lock use, so use it here so that lockdep
> knows what's going on.
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> ---
> arch/x86/xen/mmu.c |   74 +++++++++++++++++++++++++++++++++-------------------
> arch/x86/xen/mmu.h |    3 --
> 2 files changed, 48 insertions(+), 29 deletions(-)

applied to tip/x86/xen, thanks Jeremy!

	Ingo
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