| Message ID | 20231114135553.32301-4-johan+linaro@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: Fix deadlocks when enabling ASPM | expand |
On Tue, Nov 14, 2023 at 02:55:50PM +0100, Johan Hovold wrote: > The qcom_pcie_enable_aspm() helper is called from pci_walk_bus() during > host init to enable ASPM. > > Since pci_walk_bus() already holds a pci_bus_sem read lock, use the new > locked helper to enable link states in order to avoid a potential > deadlock (e.g. in case someone takes a write lock before reacquiring > the read lock). > > This issue was reported by lockdep: > > ============================================ > WARNING: possible recursive locking detected > 6.7.0-rc1 #4 Not tainted > -------------------------------------------- > kworker/u16:6/147 is trying to acquire lock: > ffffbf3ff9d2cfa0 (pci_bus_sem){++++}-{3:3}, at: pci_enable_link_state+0x74/0x1e8 > > but task is already holding lock: > ffffbf3ff9d2cfa0 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x34/0xbc > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(pci_bus_sem); > lock(pci_bus_sem); > > *** DEADLOCK *** > > Fixes: 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops") > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > Signed-off-by: Johan Hovold <johan+linaro@kernel.org> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> - Mani > --- > drivers/pci/controller/dwc/pcie-qcom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c > index ce3ece28fed2..21523115f6a4 100644 > --- a/drivers/pci/controller/dwc/pcie-qcom.c > +++ b/drivers/pci/controller/dwc/pcie-qcom.c > @@ -971,7 +971,7 @@ static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata) > { > /* Downstream devices need to be in D0 state before enabling PCI PM substates */ > pci_set_power_state(pdev, PCI_D0); > - pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL); > + pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL); > > return 0; > } > -- > 2.41.0 >
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c index ce3ece28fed2..21523115f6a4 100644 --- a/drivers/pci/controller/dwc/pcie-qcom.c +++ b/drivers/pci/controller/dwc/pcie-qcom.c @@ -971,7 +971,7 @@ static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata) { /* Downstream devices need to be in D0 state before enabling PCI PM substates */ pci_set_power_state(pdev, PCI_D0); - pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL); + pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL); return 0; }
The qcom_pcie_enable_aspm() helper is called from pci_walk_bus() during host init to enable ASPM. Since pci_walk_bus() already holds a pci_bus_sem read lock, use the new locked helper to enable link states in order to avoid a potential deadlock (e.g. in case someone takes a write lock before reacquiring the read lock). This issue was reported by lockdep: ============================================ WARNING: possible recursive locking detected 6.7.0-rc1 #4 Not tainted -------------------------------------------- kworker/u16:6/147 is trying to acquire lock: ffffbf3ff9d2cfa0 (pci_bus_sem){++++}-{3:3}, at: pci_enable_link_state+0x74/0x1e8 but task is already holding lock: ffffbf3ff9d2cfa0 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x34/0xbc other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(pci_bus_sem); lock(pci_bus_sem); *** DEADLOCK *** Fixes: 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops") Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Signed-off-by: Johan Hovold <johan+linaro@kernel.org> --- drivers/pci/controller/dwc/pcie-qcom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)