On 09/20/2017 04:39 AM, Michael Ellerman wrote: > Rob Herring <r...@kernel.org> writes: > >> On Fri, Sep 15, 2017 at 6:04 AM, abdul <abdha...@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.
So, that patch slipped past me. Not only is the parent reference not ours to drop, but when I went and looked at dlpar_cpu_add() I also noticed that of_node_put() was done on the parent prior to the call to dlpar_attach_node(). With the addition of "parent" to the dlpar_attach_node() parameter list dlpar_cpu_add() needs to be fixed up to hold the "parent" reference until after dlpar_attach_node() returns. -Tyrel > > cheers >