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From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steve Capper <steve.capper@linaro.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"gary.robertson@linaro.org" <gary.robertson@linaro.org>,
	"anders.roxell@linaro.org" <anders.roxell@linaro.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH V4 6/7] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic
Date: Thu, 1 May 2014 11:04:15 +0100	[thread overview]
Message-ID: <20140501100415.GC22316@arm.com> (raw)
In-Reply-To: <20140501095739.GO11096@twins.programming.kicks-ass.net>

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

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WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steve Capper <steve.capper@linaro.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"gary.robertson@linaro.org" <gary.robertson@linaro.org>,
	"anders.roxell@linaro.org" <anders.roxell@linaro.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH V4 6/7] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic
Date: Thu, 1 May 2014 11:04:15 +0100	[thread overview]
Message-ID: <20140501100415.GC22316@arm.com> (raw)
Message-ID: <20140501100415.SPNZXh7VvGj5A4QrIZexeRe2WXcuVUZD7BiTEghQjnk@z> (raw)
In-Reply-To: <20140501095739.GO11096@twins.programming.kicks-ass.net>

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

  parent reply	other threads:[~2014-05-01 10:04 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-28 15:01 [RFC PATCH V4 0/7] get_user_pages_fast for ARM and ARM64 Steve Capper
2014-03-28 15:01 ` Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 1/7] mm: Introduce a general RCU get_user_pages_fast Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 2/7] arm: mm: Introduce special ptes for LPAE Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 3/7] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-05-01 11:11   ` Catalin Marinas
2014-05-01 11:44     ` Steve Capper
2014-05-01 11:44       ` Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 4/7] arm: mm: Enable RCU fast_gup Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 5/7] arm64: Convert asm/tlb.h to generic mmu_gather Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 6/7] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-04-30 15:20   ` Catalin Marinas
2014-04-30 15:33     ` Catalin Marinas
2014-04-30 15:33       ` Catalin Marinas
2014-04-30 15:38       ` Steve Capper
2014-04-30 15:38         ` Steve Capper
2014-04-30 17:21         ` Catalin Marinas
2014-04-30 17:21           ` Catalin Marinas
2014-05-01  7:34           ` Steve Capper
2014-05-01  7:34             ` Steve Capper
2014-05-01  9:52             ` Catalin Marinas
2014-05-01  9:57               ` Peter Zijlstra
2014-05-01  9:57                 ` Peter Zijlstra
2014-05-01 10:04                 ` Catalin Marinas [this message]
2014-05-01 10:04                   ` Catalin Marinas
2014-05-01 10:15                   ` Steve Capper
2014-03-28 15:01 ` [RFC PATCH V4 7/7] arm64: mm: Enable RCU fast_gup Steve Capper

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