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linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 27/09/2019 03:15, Frederic Barrat wrote: > > > Le 26/09/2019 à 18:44, Andrew Donnellan a écrit : >> On 9/9/19 5:45 pm, Frederic Barrat wrote: >>> Taking a reference on the pci_dev structure was required with initial >>> commit 184cd4a3b962 ("powerpc/powernv: PCI support for p7IOC under >>> OPAL v2"), where we were storing the pci_dev in the pci_dn structure. >>> >>> However, the pci_dev was later removed from the pci_dn structure, but >>> the reference was kept. See commit 902bdc57451c ("powerpc/powernv/idoa: >>> Remove unnecessary pcidev from pci_dn"). >>> >>> The pnv_ioda_pe structure life cycle is the same as the pci_dev >>> structure, the PE is freed when the device is released. So we don't >>> need a reference for the pci_dev stored in the PE, otherwise the >>> pci_dev will never be released. Which is not really a surprise as the >>> comment (removed here as no longer needed) was stating as much. >>> >>> Fixes: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn") >>> Signed-off-by: Frederic Barrat >>> --- >>>   arch/powerpc/platforms/powernv/pci-ioda.c | 11 +---------- >>>   1 file changed, 1 insertion(+), 10 deletions(-) >>> >>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c >>> index d8080558d020..92767f006f20 100644 >>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c >>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c >>> @@ -1062,14 +1062,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev) >>>           return NULL; >>>       } >>> -    /* NOTE: We get only one ref to the pci_dev for the pdn, not for the >>> -     * pointer in the PE data structure, both should be destroyed at the >>> -     * same time. However, this needs to be looked at more closely again >>> -     * once we actually start removing things (Hotplug, SR-IOV, ...) >>> -     * >>> -     * At some point we want to remove the PDN completely anyways >>> -     */ >>> -    pci_dev_get(dev); >>>       pdn->pe_number = pe->pe_number; >>>       pe->flags = PNV_IODA_PE_DEV; >>>       pe->pdev = dev; >>> @@ -1084,7 +1076,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev) >>>           pnv_ioda_free_pe(pe); >>>           pdn->pe_number = IODA_INVALID_PE; >>>           pe->pdev = NULL; >>> -        pci_dev_put(dev); >>>           return NULL; >>>       } >>> @@ -1228,7 +1219,7 @@ static struct pnv_ioda_pe *pnv_ioda_setup_npu_PE(struct pci_dev *npu_pdev) >>>                */ >>>               dev_info(&npu_pdev->dev, >>>                   "Associating to existing PE %x\n", pe_num); >>> -            pci_dev_get(npu_pdev); >>> +            pci_dev_get(npu_pdev); // still needed after 902bdc57451c ? >> >> Did you mean to leave that comment in? > > Yes, I assumed the series wouldn't get in on the first try and a nvlink-minded developer would weigh in :) I am looking at it and I am still not so sure what exactly guarantees that lifetime(@dev) == lifetime(@pe). For example, sriov_disable() removes VFs first, and only then releases PEs so there is a window when we may have a stale pdev. Not sure. > >   Fred > > >>>               npu_pdn = pci_get_pdn(npu_pdev); >>>               rid = npu_pdev->bus->number << 8 | npu_pdn->devfn; >>>               npu_pdn->pe_number = pe_num; >>> >> > -- Alexey