linux-kernel - Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all

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Message-ID: <20100401160209.GT5825@random.random>
Date:	Thu, 1 Apr 2010 18:02:09 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	Kent Overstreet <kent.overstreet@...il.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in
 mmu_take_all_locks()

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.
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