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Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus

From Michael Ellerman <mpe@ellerman.id.au>
Newsgroups linux.kernel
Subject Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus
Date 2017-09-20 13:40 +0200
Message-ID <urLwd-2qd-5@gated-at.bofh.it> (permalink)
References <upWFr-1Yr-3@gated-at.bofh.it> <upYnT-2Ux-3@gated-at.bofh.it>
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Rob Herring <robh@kernel.org> writes:

> On Fri, Sep 15, 2017 at 6:04 AM, abdul <abdhalee@linux.vnet.ibm.com> wrote:
>> Hi,
>>
>> Mainline kernel panics during DLPAR CPU add/remove operation.
>>
>> Machine Type: Power8 PowerVM LPAR
>> kernel 4.13.0
>
> Did 4.12 work or when was it last working? I'm not seeing anything
> recent in the DT code that looks suspicious.

I'm pretty sure it's:

int dlpar_attach_node(struct device_node *dn, struct device_node *parent)
{
	int rc;

	dn->parent = parent;

	rc = of_attach_node(dn);
	if (rc) {
		printk(KERN_ERR "Failed to add device node %pOF\n", dn);
		return rc;
	}

	of_node_put(dn->parent);
HERE    ^^^^^^^^^^

	return 0;
}


Prior to 215ee763f8cb ("powerpc: pseries: remove dlpar_attach_node
dependency on full path"), we re-looked up the parent, and got another
reference on it. That meant the put before the return there was correct.
But now it's not because the caller has a reference to parent but it's
not ours to drop.

Testing a fix, will report back.

cheers

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Thread

Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Rob Herring <robh@kernel.org> - 2017-09-15 15:00 +0200
  Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Abdul Haleem <abdhalee@linux.vnet.ibm.com> - 2017-09-19 15:40 +0200
  Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Michael Ellerman <mpe@ellerman.id.au> - 2017-09-20 13:40 +0200
    Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Tyrel Datwyler <tyreld@linux.vnet.ibm.com> - 2017-09-20 19:30 +0200
      Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Michael Ellerman <mpe@ellerman.id.au> - 2017-09-21 12:00 +0200
        Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Tyrel Datwyler <tyreld@linux.vnet.ibm.com> - 2017-09-21 20:50 +0200
          Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus Michael Ellerman <mpe@ellerman.id.au> - 2017-09-22 14:00 +0200

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