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[54.240.9.37]) by mx.google.com with ESMTPS id a55si5320056qva.119.2019.02.12.08.50.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 12 Feb 2019 08:50:11 -0800 (PST) Received-SPF: pass (google.com: domain of 01000168e29daf0a-cb3a9394-e3dd-4d88-ad3c-31df1f9ec052-000000@amazonses.com designates 54.240.9.37 as permitted sender) client-ip=54.240.9.37; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug header.b=dPwog4Db; spf=pass (google.com: domain of 01000168e29daf0a-cb3a9394-e3dd-4d88-ad3c-31df1f9ec052-000000@amazonses.com designates 54.240.9.37 as permitted sender) smtp.mailfrom=01000168e29daf0a-cb3a9394-e3dd-4d88-ad3c-31df1f9ec052-000000@amazonses.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug; d=amazonses.com; t=1549990211; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=d9wM12jhuDTWdWt+Pkovf6I5uVUhrDCPMcwRg2iB6/c=; b=dPwog4Db8cxWFTs8RaPbWPHsdjVXXzK6xqpC2es8j1a9vMwSTJTBbxIqClS4bTWi jn3E5648vwwyFuDLlzLP3ebtNmQ8QHcaanGSqOxZWOF9WwuscWPvVRcezYZjIzwFHH3 zSJ0zA/tay7p90Jbs8Pdv9fCw9l9ZFY8VqBAPqsw= Date: Tue, 12 Feb 2019 16:50:11 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Alexey Kardashevskiy cc: Daniel Jordan , jgg@ziepe.ca, akpm@linux-foundation.org, dave@stgolabs.net, jack@suse.cz, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, paulus@ozlabs.org, benh@kernel.crashing.org, mpe@ellerman.id.au, hao.wu@intel.com, atull@kernel.org, mdf@kernel.org Subject: Re: [PATCH 2/5] vfio/spapr_tce: use pinned_vm instead of locked_vm to account pinned pages In-Reply-To: Message-ID: <01000168e29daf0a-cb3a9394-e3dd-4d88-ad3c-31df1f9ec052-000000@email.amazonses.com> References: <20190211224437.25267-1-daniel.m.jordan@oracle.com> <20190211224437.25267-3-daniel.m.jordan@oracle.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.02.12-54.240.9.37 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 12 Feb 2019, Alexey Kardashevskiy wrote: > Now it is 3 independent accesses (actually 4 but the last one is > diagnostic) with no locking around them. Why do not we need a lock > anymore precisely? Thanks, Updating a regular counter is racy and requires a lock. It was converted to be an atomic which can be incremented without a race.