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Subject: Re: [PATCH] PCI/hotplug: Remove unneeded of_node_put() in pnv_php
To:     Wan Jiabing <wanjiabing@vivo.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        linuxppc-dev@lists.ozlabs.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     kael_w@yeah.net
References: <20211020094604.2106-1-wanjiabing@vivo.com>
From:   Tyrel Datwyler <tyreld@linux.ibm.com>
Message-ID: <b74babe4-f3a2-15c5-b3f5-180f7f880d70@linux.ibm.com>
Date:   Wed, 20 Oct 2021 09:53:31 -0700
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On 10/20/21 2:46 AM, Wan Jiabing wrote:
> Fix following coccicheck warning:
> ./drivers/pci/hotplug/pnv_php.c:161:2-13: ERROR: probable double put.
> 
> Device node iterators put the previous value of the index variable, so
> an explicit put causes a double put.
> 
> Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>

NACK

This is a false positive from coccicheck. This is a case were a node is being
dynamically removed and the long reference needs to be dropped. Otherwise, the
reference count doesn't go to zero and trigger cleanup. This would result in us
ending up in a leaked device node.

-Tyrel

> ---
>  drivers/pci/hotplug/pnv_php.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
> index f4c2e6e01be0..f3da4f95d73f 100644
> --- a/drivers/pci/hotplug/pnv_php.c
> +++ b/drivers/pci/hotplug/pnv_php.c
> @@ -158,7 +158,6 @@ static void pnv_php_detach_device_nodes(struct device_node *parent)
>  	for_each_child_of_node(parent, dn) {
>  		pnv_php_detach_device_nodes(dn);
> 
> -		of_node_put(dn);
>  		of_detach_node(dn);
>  	}
>  }
>