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From: Andrea Arcangeli <aarcange@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Rafael Aquini <aquini@redhat.com>,
	Jon Masters <jcm@jonmasters.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Mark Salter <msalter@redhat.com>, Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] arm64: tlb: skip tlbi broadcast for single threaded TLB flushes
Date: Wed, 12 Feb 2020 07:57:57 -0500	[thread overview]
Message-ID: <20200212125757.GD3699@redhat.com> (raw)
In-Reply-To: <20200211140025.GB153117@arrakis.emea.arm.com>

Hello,

On Tue, Feb 11, 2020 at 02:00:25PM +0000, Catalin Marinas wrote:
> I think there is another race here. IIUC, the assumption you make is
> that when mm_users <= 1 && mm_count == 1, the only active user of this
> pgd/ASID is on the CPU doing the TLBI. This is not the case for
> try_to_unmap() where the above condition may be true but the active
> thread on a different CPU won't notice the local TLBI.

The "current->mm == mm" check is what shall prevent the above.

Thanks,
Andrea


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WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>, Jon Masters <jcm@jonmasters.org>,
	Rafael Aquini <aquini@redhat.com>,
	Mark Salter <msalter@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] arm64: tlb: skip tlbi broadcast for single threaded TLB flushes
Date: Wed, 12 Feb 2020 07:57:57 -0500	[thread overview]
Message-ID: <20200212125757.GD3699@redhat.com> (raw)
In-Reply-To: <20200211140025.GB153117@arrakis.emea.arm.com>

Hello,

On Tue, Feb 11, 2020 at 02:00:25PM +0000, Catalin Marinas wrote:
> I think there is another race here. IIUC, the assumption you make is
> that when mm_users <= 1 && mm_count == 1, the only active user of this
> pgd/ASID is on the CPU doing the TLBI. This is not the case for
> try_to_unmap() where the above condition may be true but the active
> thread on a different CPU won't notice the local TLBI.

The "current->mm == mm" check is what shall prevent the above.

Thanks,
Andrea



  reply	other threads:[~2020-02-12 12:58 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-03 20:17 [RFC] [PATCH 0/2] arm64: tlb: skip tlbi broadcast for single threaded TLB flushes Andrea Arcangeli
2020-02-03 20:17 ` Andrea Arcangeli
2020-02-03 20:17 ` [PATCH 1/2] mm: use_mm: fix for arches checking mm_users to optimize " Andrea Arcangeli
2020-02-03 20:17   ` Andrea Arcangeli
2020-02-18 11:31   ` Michal Hocko
2020-02-18 11:31     ` Michal Hocko
2020-02-18 18:56     ` Andrea Arcangeli
2020-02-18 18:56       ` Andrea Arcangeli
2020-02-19 11:58       ` Michal Hocko
2020-02-19 11:58         ` Michal Hocko
2020-02-19 20:04         ` Andrea Arcangeli
2020-02-19 20:04           ` Andrea Arcangeli
2020-02-03 20:17 ` [PATCH 2/2] arm64: tlb: skip tlbi broadcast for single threaded " Andrea Arcangeli
2020-02-03 20:17   ` Andrea Arcangeli
2020-02-10 17:51   ` Catalin Marinas
2020-02-10 17:51     ` Catalin Marinas
2020-02-10 20:14     ` Andrea Arcangeli
2020-02-10 20:14       ` Andrea Arcangeli
2020-02-11 14:00       ` Catalin Marinas
2020-02-11 14:00         ` Catalin Marinas
2020-02-12 12:57         ` Andrea Arcangeli [this message]
2020-02-12 12:57           ` Andrea Arcangeli
2020-02-12 14:13   ` qi.fuli
2020-02-12 14:13     ` qi.fuli
2020-02-12 15:26     ` Catalin Marinas
2020-02-12 15:26       ` Catalin Marinas

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