From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936990AbdJQQnE (ORCPT ); Tue, 17 Oct 2017 12:43:04 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:51528 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932961AbdJQQnD (ORCPT ); Tue, 17 Oct 2017 12:43:03 -0400 Subject: Re: [PATCH v8 5/8] arm64: Use of_cpu_node_to_id helper for CPU topology parsing From: Suzuki K Poulose To: Will Deacon , Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, robh@kernel.org, sudeep.holla@arm.com, frowand.list@gmail.com, devicetree@vger.kernel.org, Jonathan.Cameron@huawei.com, marc.zyngier@arm.com, peterz@infradead.org, mathieu.poirier@linaro.org, leo.yan@linaro.org, Catalin Marinas References: <20171010103303.32436-1-suzuki.poulose@arm.com> <20171010103303.32436-6-suzuki.poulose@arm.com> <20171017152422.fawwvx6e3nn4dsej@lakrids.cambridge.arm.com> <20171017161140.GD19711@arm.com> <9ecc1b51-b729-836a-5dde-c8ca9b36de40@arm.com> Message-ID: Date: Tue, 17 Oct 2017 17:42:57 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <9ecc1b51-b729-836a-5dde-c8ca9b36de40@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/10/17 17:20, Suzuki K Poulose wrote: > On 17/10/17 17:11, Will Deacon wrote: >> On Tue, Oct 17, 2017 at 04:24:23PM +0100, Mark Rutland wrote: >>> On Tue, Oct 10, 2017 at 11:33:00AM +0100, Suzuki K Poulose wrote: >>>> Make use of the new generic helper to convert an of_node of a CPU >>>> to the logical CPU id in parsing the topology. >>>> >>>> Cc: Catalin Marinas >>>> Cc: Leo Yan >>>> Cc: Will Deacon >>>> Cc: Mark Rutland >>>> Signed-off-by: Suzuki K Poulose >>> >>> This looks sane to me, but it will need an ack from Will or Catalin. >>> >>> FWIW: >>> >>> Acked-by: Mark Rutland >>> >>> Thanks, >>> Mark. >>> >>>> --- >>>>   arch/arm64/kernel/topology.c | 16 ++++++---------- >>>>   1 file changed, 6 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c >>>> index 8d48b233e6ce..21868530018e 100644 >>>> --- a/arch/arm64/kernel/topology.c >>>> +++ b/arch/arm64/kernel/topology.c >>>> @@ -37,18 +37,14 @@ static int __init get_cpu_for_node(struct device_node *node) >>>>       if (!cpu_node) >>>>           return -1; >>>> -    for_each_possible_cpu(cpu) { >>>> -        if (of_get_cpu_node(cpu, NULL) == cpu_node) { >>>> -            topology_parse_cpu_capacity(cpu_node, cpu); >>>> -            of_node_put(cpu_node); >>>> -            return cpu; >>>> -        } >>>> -    } >>>> - >>>> -    pr_crit("Unable to find CPU node for %pOF\n", cpu_node); >>>> +    cpu = of_cpu_node_to_id(cpu_node); >>>> +    if (cpu >= 0) >>>> +        topology_parse_cpu_capacity(cpu_node, cpu); >>>> +    else >>>> +        pr_crit("Unable to find CPU node for %pOF\n", cpu_node); >>>>       of_node_put(cpu_node); >> >> This of_node_put is confusing me. Since of_cpu_node_to_id appears to be >> balanced with its use of the node refcount, is this one intended to pair >> with the earlier call to of_parse_phandle? > > Yes. > >  If so, does that mainline is >> currently broken here because it doesn't drop the refcount twice for the >> matching node? > > No. This of_node_put is for the failure case where we couldn't match a CPU. > In the success case, it is dropped just before we return the result within > the loop. As we discussed offline, there is indeed a missing of_node_put() for all the nodes we loop through to match. But with this change, we have fixed that. And I don't think it is worth sending to stable. Cheers Suzuki