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Date: Thu, 1 Apr 2010 18:02:09 +0200
From: Andrea Arcangeli <aarcange@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>, Rik van Riel <riel@redhat.com>,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
       Kent Overstreet <kent.overstreet@gmail.com>,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in
 mmu_take_all_locks()
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On Thu, Apr 01, 2010 at 06:51:17PM +0300, Avi Kivity wrote:
> Can we use srcu now instead?

We can always switch to srcu. Switching to srcu is not a noop for all
mmu notifier invalidates only after these locks can schedule. At that
point, so with srcu + mutex in the rmap locks, all the mmu notifier
invalidates can schedule, allowing XPMEM to be synchronous its
invalidates, and making it safe.