From mboxrd@z Thu Jan  1 00:00:00 1970
From: catalin.marinas@arm.com (Catalin Marinas)
Date: Thu, 1 May 2014 11:04:15 +0100
Subject: [RFC PATCH V4 6/7] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic
In-Reply-To: <20140501095739.GO11096@twins.programming.kicks-ass.net>
References: <1396018892-6773-1-git-send-email-steve.capper@linaro.org>
 <1396018892-6773-7-git-send-email-steve.capper@linaro.org>
 <20140430152047.GF31220@arm.com> <20140430153317.GG31220@arm.com>
 <20140430153824.GA7166@linaro.org> <20140430172114.GI31220@arm.com>
 <20140501073402.GA30358@linaro.org>
 <20140501095246.GB22316@arm.com>
 <20140501095739.GO11096@twins.programming.kicks-ass.net>
Message-ID: <20140501100415.GC22316@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thu, May 01, 2014 at 10:57:39AM +0100, Peter Zijlstra wrote:
> On Thu, May 01, 2014 at 10:52:47AM +0100, Catalin Marinas wrote:
> > Does gup_fast walking increment the mm_users? Or is it a requirement of
> > the calling code? I can't seem to find where this happens.
> 
> No, its not required at all. One should only walk current->mm with
> gup_fast, any other usage is broken.

OK, I get it now.

> And by delaying TLB shootdown, either through disabling IRQs and
> stalling IPIs or by using RCU freeing, you're guaranteed your own page
> tables won't disappear underneath your feet.

And for RCU to work, we still need to use the full tlb_remove_table()
logic (Steve's patches just use tlb_remove_page() for table freeing).

Thanks.

-- 
Catalin